In order to test if the intestinal bacteria play an important role in antibacterial ability of earthworm, we chose Escherichia coli O157:H7, an anthropozoonosis pathogen, as a biological stressor and studied the change of intestinal bacteria community of earthworm by PCR-DGGE analysis. Results showed that the pathogen merely existed 1 - 3 days, then almost disappeared after through the earthworm’s gut. In this period, the diversity and abundance index of intestinal bacteria increased first, then decreased, and finally kept stably after 7 days. The result demonstrated that the intestinal bacteria of earthworm had ability of adjust community structure to eliminate the pathogen E. coli O157:H7, and the amount of bacteria Bacillus increased significantly, which might be the positive antagonism to E. coli O157:H7.