Polyacrylonitrile (PAN) based carbon felt is light in quality, small in specific heat capacity,soft in texture, good in adiathermancy and convenient in operation, which can save great energy. Therefore, thermal insulation of the polyacrylonitrile base is extremely superior in vacuum or inert atmosphere, in particular, performance of the polyacrylonitrile base is stable under high temperature condition, and it is the excellent thermal insulation material for Vacuum Furnace.