Abstract: The degradation of rice straw without any chemical method pretreated by a lignocellulose degradation composite microbial system XDC-2 was studied. After 6 days cultivation, exocellular xylanase activity was 335 U/mL. After 12 days, the rice straw lost 39.71% of its weight, and the weight loss of hemicellulose and cellulose were 78.27% and 14.08% respectively. The total amount of the volatile products came to a maximum in the sixth day. Four major kinds of the volatile products were determined in fermentation broth, they were acetic acid, propionic acid, butanoic acid and glycerin, which could be utilized in industrial production. The composite microbial system XDC-2 became stable in degradation process of rice straw without any chemical method pretreated according to PCR-DGGE analysis. Accordingly, it has the potential for further development and application of composite microbial system XDC-2 due to its effective ability to degrade rice straw without any chemical pretreatment.