Abstract: OBJECTIVE To study the production of AmpC enzymes and the sensitivity to antibiotics in the Enterobacteriaceae. METHODS Sixty two Enterobacteriaceae resistant to third generation cephalosporins were collected, the susceptibility to 13 kinds of antimicrobial drug and the drug tolerance to cefoxitin (FOX) were detected with K-B method. AmpC enzyme was detected by the enzyme extracts FOX three-dimensional test. And structural gene of AmpC was analyzed by PCR. RESULTS The resistant rate of 62 Enterobacteriaceae strains was low to cefepime, imipenem and amikacin, but high resistance to ampicillin/sulbactam, ceftriaxone, ceftazidime. There were 22 positive bacteria screened by FOX, 8 three-dimensional test positive bacteria; and 17 strains bacteria in which the AmpC gene were detected in the 22 screening-positive strains. CONCLUSION The resistant rate of the Enterobacteriaceae producing AmpC β-lactamases is significantly higher than those of non-producing AmpC. Imipenem or cefepime is the first-use drug for infections caused by AmpC-producing bacteria, and levofloxacin, amikacin are also effective for the treatment of such infections.