diff --git a/pkg/compute/regiondrivers/kvm.go b/pkg/compute/regiondrivers/kvm.go
index 540bfb710a..7527028a16 100644
--- a/pkg/compute/regiondrivers/kvm.go
+++ b/pkg/compute/regiondrivers/kvm.go
@@ -1433,7 +1433,8 @@ func (self *SKVMRegionDriver) RequestSyncBackupStorageStatus(ctx context.Context
 			return nil, err
 		}
 		status, _ := res.GetString("status")
-		return nil, bs.SetStatus(userCred, status, "sync status")
+		reason, _ := res.GetString("reason")
+		return nil, bs.SetStatus(userCred, status, reason)
 	})
 	return nil
 }
diff --git a/pkg/hostman/storageman/backupstorage/backup_storage.go b/pkg/hostman/storageman/backupstorage/backup_storage.go
index 8775b45063..d1e86adecc 100644
--- a/pkg/hostman/storageman/backupstorage/backup_storage.go
+++ b/pkg/hostman/storageman/backupstorage/backup_storage.go
@@ -33,7 +33,7 @@ type IBackupStorage interface {
 	ConvertFrom(srcPath string, format qemuimg.TImageFormat, backupId string) (int, error)
 	InstancePack(packageName string, backupIds []string, metadata *api.InstanceBackupPackMetadata) error
 	InstanceUnpack(packageName string) ([]string, *api.InstanceBackupPackMetadata, error)
-	IsOnline() (bool, error)
+	IsOnline() (bool, string, error)
 }
 
 var backupStoragePool *sync.Map = &sync.Map{}
diff --git a/pkg/hostman/storageman/backupstorage/backup_storage_nfs.go b/pkg/hostman/storageman/backupstorage/backup_storage_nfs.go
index fe45a0af8e..dc2a636b1c 100644
--- a/pkg/hostman/storageman/backupstorage/backup_storage_nfs.go
+++ b/pkg/hostman/storageman/backupstorage/backup_storage_nfs.go
@@ -85,7 +85,7 @@ func (s *SNFSBackupStorage) checkAndMount() error {
 	err := procutils.NewRemoteCommandContextAsFarAsPossible(ctx,
 		"mount", "-t", "nfs", fmt.Sprintf("%s:%s", s.NfsHost, s.NfsSharedDir), s.Path).Run()
 	if err != nil {
-		return ErrorBackupStorageOffline
+		return errors.Wrap(ErrorBackupStorageOffline, err.Error())
 	}
 	backupDir := s.getBackupDir()
 	if !fileutils2.Exists(backupDir) {
@@ -462,14 +462,14 @@ func (s *SNFSBackupStorage) IsExists(backupId string) (bool, error) {
 	return fileutils2.Exists(filename), nil
 }
 
-func (s *SNFSBackupStorage) IsOnline() (bool, error) {
+func (s *SNFSBackupStorage) IsOnline() (bool, string, error) {
 	err := s.checkAndMount()
 	if errors.Cause(err) == ErrorBackupStorageOffline {
-		return false, nil
+		return false, err.Error(), nil
 	}
 	if err != nil {
-		return false, err
+		return false, "", err
 	}
 	s.unMount()
-	return true, nil
+	return true, "", nil
 }
diff --git a/pkg/hostman/storageman/storagehandler/storagehandler.go b/pkg/hostman/storageman/storagehandler/storagehandler.go
index ec272159f7..29fb15f5cc 100644
--- a/pkg/hostman/storageman/storagehandler/storagehandler.go
+++ b/pkg/hostman/storageman/storagehandler/storagehandler.go
@@ -260,7 +260,7 @@ func storageSyncBackupStorage(ctx context.Context, w http.ResponseWriter, r *htt
 		hostutils.Response(ctx, w, err)
 		return
 	}
-	exist, err := backupStorage.IsOnline()
+	exist, reason, err := backupStorage.IsOnline()
 	if err != nil {
 		hostutils.Response(ctx, w, err)
 		return
@@ -275,6 +275,7 @@ func storageSyncBackupStorage(ctx context.Context, w http.ResponseWriter, r *htt
 		status = compute.BACKUPSTORAGE_STATUS_OFFLINE
 	}
 	ret.Set("status", jsonutils.NewString(status))
+	ret.Set("reason", jsonutils.NewString(reason))
 	hostutils.Response(ctx, w, ret)
 }