Abstract: Using wheat bran and straw as raw materials, optimum technology conditions of cellulase activity produced by solidstate fermentation of Trichoderma viride was optimized by orthogonal and single factor test; the effect of T. viride on cellulose degradation of wheat straw was studied. The optimum conditions were provided to the degradation of wheat straw cellulose by T. viride, and further improve the utilization rate of wheat straw. The result showed that there was significant difference in cellulase activity produced by T. viride under different conditions (P0.05). The optimal medium contained 8 g wheat straw and 2 g wheat bran, its nitrogen source was (NH4)2SO4, water content was 200%, pH value was 5.5. The optimum fermentation conditions were as follows: 96 h cultivation time, 35 ℃, pH value 6.0, 0.4% nitrogen content, 15% inoculum and semienclosed cultivation. The NDF, ADF, cellulose and hemicellulose content of wheat straw after fermentation declined by 5.22%，6.88%，4.73% and 4.16%, respectively, and there was no significant change in lignin.