For utilizing inexpensive substrate to produce cellulase,investigations of producing cellulase by solid-state fermentation with Trichoderma viride-M1 using mixture of rice straw and wheat bran were done.The results showed that the optimal solid-state fermentation conditions for cellulase were listed as follow:culture temperature was 28 ℃,the proportion of materials to water in the medium was 1∶2.5,the best nitrogen concentration was 1.5%,the ratio of rice straw to wheat bran was 7∶3;under these conditions,10% of the liquid seeds were inoculated,the cellulase activities gradually increased in 0~60 h,declined in 60~72 h,the cellulase activities increased again after 72 h,and the cellulase activities reached maximum after 108 h.