Abstract: Straw acidification pre-treatment by microorganisms can improve efficiency of methane fermentation. In order to explore the effect of different microbial communities on digestion of straw, three different microbial communities (cellulose-degrading community MC1, cellulose-degrading community WDC2 and cattle dung microbial community（CD）) were used to acidify rape straw. Effect of acidification pre-treatment on rape straw was evaluated by detecting properties changing of digestive solution during digestion process of rape straw. The results indicated that community MC1, WDC2 and CD could improve the efficiency of rape straw digestion effectively (degradation rates of rape straw were 46.77%, 44.28% and 43.40% respectively), and degradation rate increased by 12.21%-15.58% comparing with control treatments of no adding exogenous bacteria. Community MC1 and WDC2 could effectively improve COD content in the digestive solution. In 48h of digestion, COD content in solution digested by the two communities increased by 9.13% and 7.83%, respectively compared with treatments without adding exogenous bacteria. Cow manure microbial community had no capability of improving COD content in the digestive solution. In addition, compared with community MC1 and cow manure, community WDC2 could better maintain soluble sugar content in the digestive solution. Therefore，three microbial communities are cable to digest rape straw, cellulose-degrading community WDC2 has better digestion activity of rape straw and COD-producing capability comparing with community MC1 and CD.