Abstract: OBJECTIVE To investigate the situation, etiological characteristics and influencing factors of biliary tract infections in patients with obstructive jaundice in different age groups after percutaneous transhepatic cholangial drainage（PTCD）. METHODS Patients with malignant obstructive jaundice treated with PTCD in Yiwu Central Hospital from Jan. 2016 to Dec. 2019 were enrolled as the research subjects. Patients' clinical data were collected, and bile specimens were cultured for the strain identification and drug resistance analysis. The risk factors of biliary tract infections were analyzed by logistic analysis. RESULTS Thirty-five（27.34%） patients were diagnosed as biliary infections in all 128 patients. A total of 60 strains of pathogenic bacteria were detected, including 48 strains of Gram-negative bacteria（80.00%） which mainly included Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa, 10 strains of Gram-positive bacteria（16.67%） which mainly included Enterococcus faecalis, and 2 strains of fungi（3.33%）. Of the 60 strains of pathogenic bacteria, 18 were isolated from patients ≤60 years old, 26 from patients between 61 and 70 years old, and 16 from patients between 71 and 80 years old, and there was no significant difference in the detection rates of bacteria among different age groups. E.coli, K pneumoniae and P.aeruginosa were highly resistant to piperacillin, cefazolin, cefaclor, cefotaxime and ciprofloxacin, and highly sensitive to ertapenem, meropenem and imipenem. E.faecalis was highly resistant to erythromycin, tetracycline, ciprofloxacin and levofloxacin. No teicoplanin, vancomycin, or linezolid resistant strains were detected. Multivariate logistic analysis showed that age ≥60 years old, preoperative jaundice duration ≥10 d, preoperative total bilirubin ≥300 μmol/L and drainage volume ＜ 300 ml/d were independent risk factors of biliary tract infections（P＜0.05）. CONCLUSION The pathogenic bacteria associated with biliary tract infections are highly resistant to many drugs. Drug should be used according to the drug resistance spectrum. Age, preoperative condition and postoperative drainage of patients undergoing PTCD correlated to biliary tract infections. Early prevention and treatment should be carried out based on these risk factors to reduce the risk of biliary tract infection.