Abstract: OBJECTIVE To explore the risk factors for postoperative biliary tract infection in patients undergoing endoscopic retrograde cholangiopancreatography（ERCP） and observe the etiology and drug resistance genes. METHODS A total of 182 patients who underwent ERCP in Hanchuan People's Hospital from May 2018 to Oct 2020 were recruited as the study subjects and divided into the biliary tract infection group with 37 cases and the non-infection group with 145 cases according to the status of biliary tract infection after ERCP. The clinical data were compared between the two groups of patients. Logistic regression analysis was carried out for risk factors for the postoperative biliary tract infection, the bile specimens were collected from the patients with biliary tract infection so as to conduct the bacterial culture, the drug susceptibility testing was performed, and the genotypes of drug resistance genes were identified. RESULTS The proportions of patients with upper biliary tract obstruction, duration of ERCP more than 1 hour, poor bile drainage after surgery, Oddi sphincter dysfunction and paraduodenal diverticula were higher in the biliary tract infection group than in the non-infection group, while the proportion of patients who were treated with antibiotics prophylaxis after ERCP was lower in the biliary tract infection group than in the non-infection group（P＜0.05）. Multivariate logistic regression analysis showed that the upper biliary tract obstruction, Oddi sphincter dysfunction and paraduodenal diverticula were the risk factors for postoperative infection in the patients undergoing ERCP（P＜0.05）. Totally 44 strains of pathogens were isolated, 23（52.27%） of which were Escherichia coli, including 18 strains of extended-spectrum β-lactamases（ESBLs）-producing E.coli and 5 strains that did not produced ESBLs. There were significant differences in the drug resistance rates to β-lactams and quinolones between the two（P＜0.05）; both were completely sensitive to carbapenems. There were significant differences in the drug resistance genotypes between the ESBLs-producing strains and the strains that did not produced ESBLs（P＜0.05）. CONCLUSION E.coli is the predominant species among the pathogens isolated from the ERCP patients with postoperative biliary tract infection, the ESBLs-producing E.coli shows the multi-drug resistance. bla_TEM and bla_CTX-M are the major drug resistance genotypes. It is necessary for the hospital to focus on the prevention of high risk factors.