A mutation of wild strain ,Trichoderma Viride, Tr-02 irradiated by laser was studied in this paper. A high xylanase-producing strain was obtained by two steps oriental screening finally. The results show that an optimization condition of the xylanase fermentation is as following: 0.5% corncob as the carbon source, 0.5% peptone as the nitrogen source, 0.1% Tween-80 as a enzyme-promoting agent, initial medium pH to 5.0, medium volume to 100mL, vaccinated two rings of spores, 28℃, 180 r/min, fermented 48h. The xylanase activity of the mutant reaches 281.21U/mL and is 31.83% higher than that of the original strain under the same conditions.