In order to assess the changes of the intestinal microbial community after the feeding conversion of grass carp(Ctenopharyngodon idellus),we analyzed the intestinal microbial communities of grass carp by PCR-DGGE.The results indicated that there were significant differences among the intestinal microbial communities from the grass carps caught in different months.However,the sample size and fullness were not detected to have significant correlation with the intestinal microbial community,which were generally recognized as the factors influencing the intestinal microbial community.These results implied that environmental difference probably is the most important factor influencing the intestinal microbial community in a short-term.Our results will provide the basic information to elucidate the change rule of intestinal microbial community of grass carp,and the action mechanism of the intestinal probiotics,the relationship between intestinal microbes and the fish diseases.