diff --git a/cmd/lotus-seed/seed/seed.go b/cmd/lotus-seed/seed/seed.go
index c4fa580bf..858db9720 100644
--- a/cmd/lotus-seed/seed/seed.go
+++ b/cmd/lotus-seed/seed/seed.go
@@ -84,6 +84,10 @@ func PreSeal(maddr address.Address, ssize uint64, sectors int, sbroot string, pr
 			return nil, xerrors.Errorf("commit: %w", err)
 		}
 
+		if err := sb.TrimCache(sid); err != nil {
+			return nil, xerrors.Errorf("trim cache: %w", err)
+		}
+
 		log.Warn("PreCommitOutput: ", sid, pco)
 		sealedSectors = append(sealedSectors, &genesis.PreSeal{
 			CommR:    pco.CommR,
diff --git a/lib/sectorbuilder/files.go b/lib/sectorbuilder/files.go
index c19fb3861..373741cc8 100644
--- a/lib/sectorbuilder/files.go
+++ b/lib/sectorbuilder/files.go
@@ -3,8 +3,10 @@ package sectorbuilder
 import (
 	"fmt"
 	"io"
+	"io/ioutil"
 	"os"
 	"path/filepath"
+	"strings"
 	"sync"
 
 	"golang.org/x/xerrors"
@@ -61,6 +63,33 @@ func (sb *SectorBuilder) GetPath(typ string, sectorName string) (string, error)
 	}
 }
 
+func (sb *SectorBuilder) TrimCache(sectorID uint64) error {
+	dir, err := sb.sectorCacheDir(sectorID)
+	if err != nil {
+		return xerrors.Errorf("getting cache dir: %w", err)
+	}
+
+	files, err := ioutil.ReadDir(dir)
+	if err != nil {
+		return xerrors.Errorf("readdir: %w", err)
+	}
+
+	for _, file := range files {
+		if !strings.HasSuffix(file.Name(), ".dat") { // _aux probably
+			continue
+		}
+		if strings.HasSuffix(file.Name(), "-data-tree-r-last.dat") { // Want to keep
+			continue
+		}
+
+		if err := os.Remove(filepath.Join(dir, file.Name())); err != nil {
+			return xerrors.Errorf("rm %s: %w", file.Name(), err)
+		}
+	}
+
+	return nil
+}
+
 func toReadableFile(r io.Reader, n int64) (*os.File, func() error, error) {
 	f, ok := r.(*os.File)
 	if ok {
diff --git a/lib/sectorbuilder/sectorbuilder_test.go b/lib/sectorbuilder/sectorbuilder_test.go
index cc8cb9563..36520374e 100644
--- a/lib/sectorbuilder/sectorbuilder_test.go
+++ b/lib/sectorbuilder/sectorbuilder_test.go
@@ -240,6 +240,10 @@ func TestSealPoStNoCommit(t *testing.T) {
 		t.Fatalf("%+v", err)
 	}
 
+	if err := sb.TrimCache(1); err != nil {
+		t.Fatal(err)
+	}
+
 	genCandidiates := post(t, sb, s)
 
 	epost := time.Now()