My ArcScene menubar is disappeared. I am trying multiple time to fix it but failed.
Can anyone help me to fix it?
Your symptoms suggest that returning ArcScene to its factory settings may be worth considering. To reset ArcScene you can delete or rename your Normal.sxt (in a similar fashion to how you may reset ArcMap via its Normal.mxt).
The Online Help page entitled About configuring the user interface describes where to find these templates:
The Normal templates—Normal.mxt (ArcMap), Normal.gxt (ArcCatalog), Normal.3dt (ArcGlobe), and Normal.sxt (ArcScene)—are located in your user settings folder. For example, in Windows 2000 or XP, the ArcMap Normal.mxt can be found in C:\Documents and Settings\\Application Data\ESRI\Desktop10.0\ArcMap\Templates, and in Windows Vista, it can be found in C:\Users\\AppData\Roaming\ESRI\Desktop10.0\ArcMap\Templates.