follow code.

         SwSktSeg.Select2 True, 0 →  can be select

         Set SwFeat = SwSelMgr.GetSelectedObject5(1) → don't set SwFeat

*****************************************************

Private Sub ll()

   Dim SwApp As SldWorks.SldWorks, SwModel As ModelDoc2

      Set SwApp = Application.SldWorks

      Set SwModel = SwApp.ActiveDoc

   Dim SwSelMgr As SelectionMgr

      Set SwSelMgr = SwModel.SelectionManager

   Dim SwSktSeg  As SketchSegment, SwFeat As Feature, SwSketch As Sketch

      With SwModel

         'tmp = .Extension.SelectByID2("上视基准面", "PLANE", 0, 0, 0, False, 0, Nothing, 0)

         tmp = .Extension.SelectByID2("上视", "PLANE", 0, 0, 0, False, 0, Nothing, 0)

         Set SwSktSeg = .CreateCircleByRadius2(0, 0, 0, 24)       

         SwSktSeg.Select True

         SwSktSeg.GetSketch       

         .InsertSketch2 True

         Set SwSketch = SwSktSeg.GetSketch

         SwSktSeg.Select2 True, 0

         Stop

         Set SwFeat = SwSelMgr.GetSelectedObject5(1)

      End With

End Sub