Abstract: Pre\|treatment by acidification and hydrolysis is the key technique for biomethanation process. In order to improve the degradation efficiency of rice straw by diacolation process， the reaction condition was optimized from solid\|fluid ratio， fermentation temperature， urea concentration， and Tween\|80 dosage. It was shown that optimum condition was as follows: solid\|fluid ratio of 1∶8， fermentation temperature of 37℃， urea concentration of 3%， and Tween\|80 concentration of 02%. During the degradation， the pH of the reaction system was maintained at 70-75. Hemicellulose in rice straw was largely degraded after the process， and cellulose and lignin were degraded to varying degrees. Electronic scanning image displayed that the compact structure of rice straw surface mastoid was destroyed， and deep long cells were exposed and disintegrated to some extent.

Key words: rice straw, EM bacteria, biodegradation, methane gas