Porous composite of $Al_2O_3$ and AIN based mullite and SiC can be prepared by alumium reaction synthesis and atmosphere controllied sintering in order to improve the durability of a gas filter body. The porous $Al_2O_3$-AIN-mullite, which has a strength of 168 kg/$ extrm{cm}^2$ and porosity of 51.59%, could be obtained by stmospheric firing at $1600^{circ}C$ and the porous $Al_2O_3$-AIN-SiC with a porosity of 33% and strength of 977 kg/$ extrm{cm}^2$, could also be prepared. The average pore size has been changed from 0.2$mu extrm{m}$ in a reduction atmosphere and to 2$mu extrm{m}$ in an air atmosphere, respectively.