The present study was evaluated the antibacterial effect of the combination of Coptidis rhizoma,Lonicerae Flos, and Paeonia japonica (1:1:1) extracts (CLP1000). Also, the effectiveness of CLP1000, dioctahedral smectite (DHS), and the combination of CLP1000 and DHS (CLPS1000) against E. coli O157:H7 infection was studied using ICR female mice. During the incubation period, the dose of 10% and 20% CLP1000 were inhibited the growth of E. coli O157:H7 by 30% and 47%, respectively. For 7 days after single challenge with E. coli O157:H7, forty female ICR mice were divided into four experimental groups which were orally administered with saline, 10% CLP1000, 10% DHS, and 10% CLPS1000, respectively. On the 3rd day, the number of E. coli O157:H7 in mouse feces was significantly decreased by administration of CLP1000 (p < 0.05), DHS (p < 0.05) and CLPS1000 (p < 0.001). On the 7th day, CLP1000 (p < 0.05) and CLPS1000 (p < 0.001) administration significantly decreased the number of E. coli O157:H7. According to the results of the present study, administration of CLPS1000 to mice can reduce the severity of E. coli O157:H7 infection. Also, it is suggested that CLPS100 represents a good candidate for the treatment of enteric infections in domestic animals.