Abstract: The vacuum electronic device is one of most important devices in electronic industy. It must be good vacuum density，fine mechanical strength，and excellent insulation property etc. Sometimes also require 20 years of life（. For example，vaccum switch tube）. Now the high aluminum oxide ceramics and active Mo －Mn process have been used almost all over the world. The products made in China have some defects. In this paper，the causes of defects are systematically studied and analyed and the corresponding improvement measures are put forward.
Key words: Aluminum Oxide Powder；High Aluminum Oxide Ceramics；Vacuum Electronic Ceramics；Vaccum Switch Tube