Corn straw was hydrolyzed by cellulose compound enzyme after steam explosion pretreatment with H2SO4 and NH3OH. The hydrolyzate was fermented to produce γ-PGA. Through single factor and orthogonal experiment,sugar content was used as index to investigate the effects of various factors on the enzymatic hydrolysis after pretreatment with 1. 0% H2SO4,10. 0% NH3 OH and water. The results indicated that the best conditions for these three kinds of enzymatic pretreatments of corn stover were almost the same as follows: the amount of enzyme was 35 FPIU /g,substrate concentration was 1∶ 15,reaction time was 96 h. The optimal ratio of corn stover saccharification solution to corn hydrolyzate for production of γ-PGA was 7 ∶ 3. The production of γ-PGA in mixed fermentation increased by95. 12% compared to fermentation with corn hydrolyzate alone.