Abstract: The objective of this study was to investigate the prevalence of antimicrobial resistance and aminoglycosides resistance genes(aadA1,aaC2, aaC4 and aphA3) among 480 commensal Escherichia coli isolates, which were collected from weaning piglets of 95 large scale pig farms among 19 provinces in China from 2006 to 2007.The resistance of those E.coli strains toward 19 broadspectrum antibiotics were tested by K-B(Kirby-Bauer) method, and 4 aminoglycosides resistance genes were detected by multiplex PCR. The results showed that E.coli isolates were relatively sensitive to polymycin B (85.6%)，cefotaxime sodium (85.3%)，amikacin (84.8%) and spectinomycine (65.0%) Most of 480 isolates were multidrug resistant strains. The number of E-coli isolates, which were resistant to 13，14，15，16 or 17 antibiotics, was relatively more than others. Moreover, there were 26 isolates resistant to 18 antibiotics and 14 isolates resistant to 19 antibiotics. By WHONET5.4 analysis, the number of swine farms resistant to amikacin,cefotaxime sodium and polymycin B was relatively less than others, and they were 29,26 and 24, respectively. The mainly detected aminoglycosides resistance genes were aadA1(65.89%), aaC2(52.35%)，aaC4(12.91%) and aphA3(10.95%). The antimicrobial resistance genetype of aadA1/aaC2(29.61%) and aadA1(18.04%) were detected frequently among commensal E-coli isolates. The antimicrobial resistance genotype of aadA1/aaC2(43), aadA1/aaC2/aaC4(20) and aadA1/aaC2/aaC4/aphA3(20) were relatively prevalent among 95 pig farms by excel analysis. By comparing the coincidence rate of antimicrobial resistant phenotype and genes, the coincidence rate of amikacin(68.39%) was relatively higher than other antibiotics. The results indicated that the commensal E-coli could produce multidrug resistant to antibiotics, be potential reservoir to preserve and disseminate antimicrobial resistance genes between pathogenic and nonpathogenic bacteria, and could be used as indicator to survey antimicrobial resistance in swine farm environment.