diff --git a/cmd/geth/main.go b/cmd/geth/main.go
index e6d1128ba..a94c0c17d 100644
--- a/cmd/geth/main.go
+++ b/cmd/geth/main.go
@@ -86,6 +86,7 @@ var (
 		utils.TxPoolGlobalQueueFlag,
 		utils.TxPoolLifetimeFlag,
 		utils.SyncModeFlag,
+		utils.SyncTargetFlag,
 		utils.ExitWhenSyncedFlag,
 		utils.GCModeFlag,
 		utils.SnapshotFlag,
diff --git a/cmd/utils/flags.go b/cmd/utils/flags.go
index d705d7a16..974c03579 100644
--- a/cmd/utils/flags.go
+++ b/cmd/utils/flags.go
@@ -18,6 +18,7 @@
 package utils
 
 import (
+	"bytes"
 	"context"
 	"crypto/ecdsa"
 	"errors"
@@ -36,10 +37,12 @@ import (
 	"github.com/ethereum/go-ethereum/accounts/keystore"
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/common/fdlimit"
+	"github.com/ethereum/go-ethereum/common/hexutil"
 	"github.com/ethereum/go-ethereum/consensus/ethash"
 	"github.com/ethereum/go-ethereum/core"
 	"github.com/ethereum/go-ethereum/core/rawdb"
 	"github.com/ethereum/go-ethereum/core/txpool"
+	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/core/vm"
 	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/eth"
@@ -68,6 +71,7 @@ import (
 	"github.com/ethereum/go-ethereum/p2p/nat"
 	"github.com/ethereum/go-ethereum/p2p/netutil"
 	"github.com/ethereum/go-ethereum/params"
+	"github.com/ethereum/go-ethereum/rlp"
 	"github.com/ethereum/go-ethereum/rpc"
 	pcsclite "github.com/gballet/go-libpcsclite"
 	gopsutil "github.com/shirou/gopsutil/mem"
@@ -664,11 +668,18 @@ var (
 		Category: flags.LoggingCategory,
 	}
 
+	// MISC settings
 	IgnoreLegacyReceiptsFlag = &cli.BoolFlag{
 		Name:     "ignore-legacy-receipts",
 		Usage:    "Geth will start up even if there are legacy receipts in freezer",
 		Category: flags.MiscCategory,
 	}
+	SyncTargetFlag = &cli.PathFlag{
+		Name:      "synctarget",
+		Usage:     `File for containing the hex-encoded block-rlp as sync target(dev feature)`,
+		TakesFile: true,
+		Category:  flags.MiscCategory,
+	}
 
 	// RPC settings
 	IPCDisabledFlag = &cli.BoolFlag{
@@ -1874,6 +1885,25 @@ func SetEthConfig(ctx *cli.Context, stack *node.Node, cfg *ethconfig.Config) {
 			cfg.EthDiscoveryURLs = SplitAndTrim(urls)
 		}
 	}
+	if ctx.IsSet(SyncTargetFlag.Name) {
+		path := ctx.Path(SyncTargetFlag.Name)
+		if path == "" {
+			Fatalf("Failed to resolve file path")
+		}
+		blob, err := os.ReadFile(path)
+		if err != nil {
+			Fatalf("Failed to read block file: %v", err)
+		}
+		rlpBlob, err := hexutil.Decode(string(bytes.TrimRight(blob, "\r\n")))
+		if err != nil {
+			Fatalf("Failed to decode block blob: %v", err)
+		}
+		var block types.Block
+		if err := rlp.DecodeBytes(rlpBlob, &block); err != nil {
+			Fatalf("Failed to decode block: %v", err)
+		}
+		cfg.SyncTarget = &block
+	}
 	// Override any default configs for hard coded networks.
 	switch {
 	case ctx.Bool(MainnetFlag.Name):
@@ -2027,6 +2057,13 @@ func RegisterEthService(stack *node.Node, cfg *ethconfig.Config) (ethapi.Backend
 		Fatalf("Failed to register the Engine API service: %v", err)
 	}
 	stack.RegisterAPIs(tracers.APIs(backend.APIBackend))
+
+	// Register the auxiliary full-sync tester service in case the sync
+	// target is configured.
+	if cfg.SyncTarget != nil && cfg.SyncMode == downloader.FullSync {
+		ethcatalyst.RegisterFullSyncTester(stack, backend, cfg.SyncTarget)
+		log.Info("Registered full-sync tester", "number", cfg.SyncTarget.NumberU64(), "hash", cfg.SyncTarget.Hash())
+	}
 	return backend.APIBackend, backend
 }
 
diff --git a/eth/catalyst/tester.go b/eth/catalyst/tester.go
new file mode 100644
index 000000000..63ee5feb2
--- /dev/null
+++ b/eth/catalyst/tester.go
@@ -0,0 +1,100 @@
+// Copyright 2022 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package catalyst
+
+import (
+	"sync"
+	"time"
+
+	"github.com/ethereum/go-ethereum/core/beacon"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/eth"
+	"github.com/ethereum/go-ethereum/log"
+	"github.com/ethereum/go-ethereum/node"
+)
+
+// FullSyncTester is an auxiliary service that allows Geth to perform full sync
+// alone without consensus-layer attached. Users must specify a valid block as
+// the sync target. This tester can be applied to different networks, no matter
+// it's pre-merge or post-merge, but only for full-sync.
+type FullSyncTester struct {
+	api    *ConsensusAPI
+	block  *types.Block
+	closed chan struct{}
+	wg     sync.WaitGroup
+}
+
+// RegisterFullSyncTester registers the full-sync tester service into the node
+// stack for launching and stopping the service controlled by node.
+func RegisterFullSyncTester(stack *node.Node, backend *eth.Ethereum, block *types.Block) (*FullSyncTester, error) {
+	cl := &FullSyncTester{
+		api:    NewConsensusAPI(backend),
+		block:  block,
+		closed: make(chan struct{}),
+	}
+	stack.RegisterLifecycle(cl)
+	return cl, nil
+}
+
+// Start launches the full-sync tester by spinning up a background thread
+// for keeping firing NewPayload-UpdateForkChoice combos with the provided
+// target block, it may or may not trigger the beacon sync depends on if
+// there are protocol peers connected.
+func (tester *FullSyncTester) Start() error {
+	tester.wg.Add(1)
+	go func() {
+		defer tester.wg.Done()
+
+		ticker := time.NewTicker(time.Second * 5)
+		defer ticker.Stop()
+
+		for {
+			select {
+			case <-ticker.C:
+				// Don't bother downloader in case it's already syncing.
+				if tester.api.eth.Downloader().Synchronising() {
+					continue
+				}
+				// Short circuit in case the target block is already stored
+				// locally.
+				if tester.api.eth.BlockChain().HasBlock(tester.block.Hash(), tester.block.NumberU64()) {
+					log.Info("Full-sync target reached", "number", tester.block.NumberU64(), "hash", tester.block.Hash())
+					return
+				}
+				// Shoot out consensus events in order to trigger syncing.
+				data := beacon.BlockToExecutableData(tester.block)
+				tester.api.NewPayloadV1(*data)
+				tester.api.ForkchoiceUpdatedV1(beacon.ForkchoiceStateV1{
+					HeadBlockHash:      tester.block.Hash(),
+					SafeBlockHash:      tester.block.Hash(),
+					FinalizedBlockHash: tester.block.Hash(),
+				}, nil)
+			case <-tester.closed:
+				return
+			}
+		}
+	}()
+	return nil
+}
+
+// Stop stops the full-sync tester to stop all background activities.
+// This function can only be called for one time.
+func (tester *FullSyncTester) Stop() error {
+	close(tester.closed)
+	tester.wg.Wait()
+	return nil
+}
diff --git a/eth/ethconfig/config.go b/eth/ethconfig/config.go
index 756063393..e9651d041 100644
--- a/eth/ethconfig/config.go
+++ b/eth/ethconfig/config.go
@@ -32,6 +32,7 @@ import (
 	"github.com/ethereum/go-ethereum/consensus/ethash"
 	"github.com/ethereum/go-ethereum/core"
 	"github.com/ethereum/go-ethereum/core/txpool"
+	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/eth/downloader"
 	"github.com/ethereum/go-ethereum/eth/gasprice"
 	"github.com/ethereum/go-ethereum/ethdb"
@@ -211,6 +212,10 @@ type Config struct {
 
 	// OverrideTerminalTotalDifficultyPassed (TODO: remove after the fork)
 	OverrideTerminalTotalDifficultyPassed *bool `toml:",omitempty"`
+
+	// SyncTarget defines the target block of sync. It's only used for
+	// development purposes.
+	SyncTarget *types.Block
 }
 
 // CreateConsensusEngine creates a consensus engine for the given chain configuration.
diff --git a/eth/ethconfig/gen_config.go b/eth/ethconfig/gen_config.go
index 514facde0..a3dcf5a12 100644
--- a/eth/ethconfig/gen_config.go
+++ b/eth/ethconfig/gen_config.go
@@ -10,6 +10,7 @@ import (
 	"github.com/ethereum/go-ethereum/consensus/ethash"
 	"github.com/ethereum/go-ethereum/core"
 	"github.com/ethereum/go-ethereum/core/txpool"
+	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/eth/downloader"
 	"github.com/ethereum/go-ethereum/eth/gasprice"
 	"github.com/ethereum/go-ethereum/miner"
@@ -63,6 +64,7 @@ func (c Config) MarshalTOML() (interface{}, error) {
 		CheckpointOracle                      *params.CheckpointOracleConfig `toml:",omitempty"`
 		OverrideTerminalTotalDifficulty       *big.Int                       `toml:",omitempty"`
 		OverrideTerminalTotalDifficultyPassed *bool                          `toml:",omitempty"`
+		FullSyncTarget                        *types.Block
 	}
 	var enc Config
 	enc.Genesis = c.Genesis
@@ -109,6 +111,7 @@ func (c Config) MarshalTOML() (interface{}, error) {
 	enc.CheckpointOracle = c.CheckpointOracle
 	enc.OverrideTerminalTotalDifficulty = c.OverrideTerminalTotalDifficulty
 	enc.OverrideTerminalTotalDifficultyPassed = c.OverrideTerminalTotalDifficultyPassed
+	enc.FullSyncTarget = c.SyncTarget
 	return &enc, nil
 }
 
@@ -159,6 +162,7 @@ func (c *Config) UnmarshalTOML(unmarshal func(interface{}) error) error {
 		CheckpointOracle                      *params.CheckpointOracleConfig `toml:",omitempty"`
 		OverrideTerminalTotalDifficulty       *big.Int                       `toml:",omitempty"`
 		OverrideTerminalTotalDifficultyPassed *bool                          `toml:",omitempty"`
+		FullSyncTarget                        *types.Block
 	}
 	var dec Config
 	if err := unmarshal(&dec); err != nil {
@@ -296,5 +300,8 @@ func (c *Config) UnmarshalTOML(unmarshal func(interface{}) error) error {
 	if dec.OverrideTerminalTotalDifficultyPassed != nil {
 		c.OverrideTerminalTotalDifficultyPassed = dec.OverrideTerminalTotalDifficultyPassed
 	}
+	if dec.FullSyncTarget != nil {
+		c.SyncTarget = dec.FullSyncTarget
+	}
 	return nil
 }