The susceptibility to 9 kinds of antibiotics of 393 animal pathogenic E. coli isolated from clinical samples was determined from 2000 to 2003. The resistance to TC, GM, CMP, AMP, RA, KM, FT, SM and CIP were 93.89%, 57.76%,78.63%, 77.86%, 92.11% ,47.33%, 46.82%, 76.84% and 74.81%, respectively. The isolates could be classified into eight classes according to the number of drugs to which srains were resistant. The resistance spectrum of the isolates varied from 2to 9 kinds of the above drugs. The strains that were resistant to seven kinds of drugs were more than 80 percent. The resistance rates of swine origin strains to GM,AMP and KM were higher than those of poultry origin strains, while the resistance rates of poultry origin strains to TC, CMP, SM and CIP were higher remarkably than those of swine origins. The frequency of resistance increased from 2000 to 2003,which was from 67.33% to 90.58% for CMP, 71.29% to 84.81% for AMP, 73.76%to 80.10% for SM and 61.88% to 88.48% for CIP. At the same time, the resistance rate of GM decreased from 61.39% to 53.92%. Thirty-seven strains (95 %) could make all the Kunming mice die within 72 h injected intraperitoneally with the culmice three times in vivo. The pathogenicity of wild strains with drug resistance acquired naturaly to mice did not decline.