Abstract: In order to understand the microbial degradation of steam exploded cotton stalks, the microbial fermentation period and fermentation technical parameters were studied. Curves of cellulase activity were built to determine the microbial fermentation period of steam exploded cotton stalks, and on the basis of single factors experiments, orthogonal experiment was designed to optimize the fermentation technical parameters. The results revealed that the microbial degradation of steam exploded cotton stalks started quickly, at the 4th day of the fermentation process, CMCase and FPase gained the highest value, so 4-day-stage was determined as the fermentation period. Factors as nitrogen source, fermentation temperature, original pH value and inoculation quantity set in process of steam exploded cotton stalks degradation showed very significant effects on CMCase and glycosylated ratio. Effects of nitrogen source on FPase and cellulose-decomposing ratio reached very significant levels, and the original pH value affected the cellulose-decomposing ratio significantly, while other factors had no significant affect. Considering the effects of all the four factors on cellulase production, glycosylation and cellulose-degradation of steam exploded cotton stalks, the optimized technical conditions were gained: bran extract as nitrogen source, temperature at 30℃, original pH value at 6.5, inoculation quantity at 1.0%. The research results provide technical reference for further exploitation of cotton stalks.