ObjectiveTo investigate whether antimicrobial use before endoscopic retrograde cholangiopancreatography (ERCP) can decrease postERCP cholangitis rate.Methods138 patients with hilar cholangiocarcinoma were randomly grouped into experimental group (67 cases) and control group(71 cases). Patients in experimental group accepted intravenous injection of cefoperazone sodium 1.0 g 30 min before ERCP, control group were treated routinely and without using antimicrobial agents.ResultsThere was no significant difference in general clinical data between two groups(P>0.05). After receiving ERCP, cholangitis rate in experimental group and contro group was 34.33%（23/67） and 26.76%（19/71）respectively, there was no significant difference between two groups (χ2=0.360, P=0.152).ConclusionPreERCP antimicrobial use is not ideal for decreasing postERCP cholangitis rate.