diff --git a/dm/relay/binlog_writer.go b/dm/relay/binlog_writer.go
index 1f503935dae..8bbc67b9f0e 100644
--- a/dm/relay/binlog_writer.go
+++ b/dm/relay/binlog_writer.go
@@ -36,12 +36,15 @@ const (
 // BinlogWriter is a binlog event writer which writes binlog events to a file.
 // Open/Write/Close cannot be called concurrently.
 type BinlogWriter struct {
-	offset   atomic.Int64
-	file     *os.File
-	relayDir string
-	uuid     atomic.String
-	filename atomic.String
-	err      atomic.Error
+	// offset means the offset we add to binlog writer
+	offset atomic.Int64
+	// fileOffset means the offset we finish write to the file
+	fileOffset atomic.Int64
+	file       *os.File
+	relayDir   string
+	uuid       atomic.String
+	filename   atomic.String
+	err        atomic.Error
 
 	logger log.Logger
 
@@ -98,6 +101,7 @@ func (w *BinlogWriter) run() {
 			errOccurs = true
 			return
 		}
+		w.fileOffset.Add(int64(n))
 		buf.Reset()
 	}
 
@@ -136,7 +140,9 @@ func (w *BinlogWriter) Open(uuid, filename string) error {
 		return terror.ErrBinlogWriterGetFileStat.Delegate(err, f.Name())
 	}
 
-	w.offset.Store(fs.Size())
+	size := fs.Size()
+	w.offset.Store(size)
+	w.fileOffset.Store(size)
 	w.file = f
 	w.uuid.Store(uuid)
 	w.filename.Store(filename)
@@ -168,6 +174,7 @@ func (w *BinlogWriter) Close() error {
 
 	w.file = nil
 	w.offset.Store(0)
+	w.fileOffset.Store(0)
 	w.uuid.Store("")
 	w.filename.Store("")
 	w.input = nil
@@ -204,5 +211,5 @@ func (w *BinlogWriter) Offset() int64 {
 }
 
 func (w *BinlogWriter) isActive(uuid, filename string) (bool, int64) {
-	return uuid == w.uuid.Load() && filename == w.filename.Load(), w.offset.Load()
+	return uuid == w.uuid.Load() && filename == w.filename.Load(), w.fileOffset.Load()
 }