A strain Trichoderma viride ZC producing extracellular neutral cellulase was screened. The effect of various carbon source, mixed carbon source, and ratio of corn fibre to wheat bran on enzyme activity in shaking flasks was investigated. Fermentation culture medium with 4 g/dL corn fibre and 1 g/dL wheat bran was selected. Enzyme avtivity can reach 321.12 U/mL in the culture medium.