diff --git a/nodedb.go b/nodedb.go
index ed813301e..ea26fc821 100644
--- a/nodedb.go
+++ b/nodedb.go
@@ -14,8 +14,9 @@ import (
 )
 
 const (
-	int64Size = 8
-	hashSize  = sha256.Size
+	int64Size      = 8
+	hashSize       = sha256.Size
+	genesisVersion = 1
 )
 
 var (
@@ -168,12 +169,31 @@ func (ndb *nodeDB) SaveBranch(node *Node) []byte {
 	node._hash()
 	ndb.SaveNode(node)
 
+	// resetBatch only working on generate a genesis block
+	if node.version <= genesisVersion {
+		ndb.resetBatch()
+	}
 	node.leftNode = nil
 	node.rightNode = nil
 
 	return node.hash
 }
 
+// resetBatch reset the db batch, keep low memory used
+func (ndb *nodeDB) resetBatch() {
+	var err error
+	if ndb.opts.Sync {
+		err = ndb.batch.WriteSync()
+	} else {
+		err = ndb.batch.Write()
+	}
+	if err != nil {
+		panic(err)
+	}
+	ndb.batch.Close()
+	ndb.batch = ndb.db.NewBatch()
+}
+
 // DeleteVersion deletes a tree version from disk.
 func (ndb *nodeDB) DeleteVersion(version int64, checkLatestVersion bool) error {
 	ndb.mtx.Lock()