L.casei Zhang soliquoid were fed to mice, after the mice were counteracted toxic E.coli O157 and k88，we observed the incidence of mice.We obtained the intestinal contents of mice in control groups and feeding oral lactobacilli groups which were live at the fourth day after they were counteracted toxic Escherichia coli O157 and K88, E.coli and Lactobacillus which were in intestinal contents were isolated and purified by selective medium, and the total DNA of isolated bacterium was extracted, then amplified by ERIC-PCR. We found that Feeden by L.casei Zhang can reduce the death rate of mice which were counteracted toxic E.coliO157 and k88. After stop feeding lactobacilli at the fourth day, L.casei Zhang was isolated from intestinal tract of mice, But E.coliO157 and k88 wasn't isolated from groups of fed L.casei Zhang. The sum total of E.coli of fed L.casei Zhang compared with the sum total of E.coli of control groups were low significant(P<0.01)very much. The results indicated that L.casei Zhang can adhere and grow in the gut of mice and play a part in protection to mice.