Fibrous alumina ceramics with ultra-high porosity(65-85%)were fabricated through a process of mixing the slurry of alumina fibers and a binder,vacuum-molding and sintering the dried felt.Such birds nestlike structure has the advantage of low density,low thermal conductivity and reasonable high mechanical strength,which can be used as thermal insulations.The effects of porosity on the room-temperature thermal conductivity and mechanical properties of the fibrous ceramics were studied.