Abstract: OBJECTIVE To explore the clinical value of o-phthalaldehyde in prevention of postoperative infection in endoscopic retrograde cholangiopancreatography (ERCP) patients. METHODS A total of 1000 patients with pancreaticobiliary diseases who were treated in gastroenterology department and were supposed to received ERCP from Jan 2014 to Dec 2016 were enrolled in the study and randomly divided into the observation group and the control group, with 500 cases in each group. The control group was treated with glutaraldehyde for disinfection, while the observation group was treated with o-phthalaldehyde for disinfection. 50 endoscopes were randomly drawn from each group so as to evaluate the effects of disinfection. The disinfection time, endoscopic appointment time and total amount of disinfection were statistically analyzed. The types of postoperative infection, incidence of infection and species of pathogens were observed and compared between the two groups of patients. RESULTS The colony counts and total colony counts of pathogens of the observation group were significantly less than those of the control group after the disinfection (P<0.05). The qualified rate of disinfection of endoscopes was as high as 100.00%. The disinfection time and appointment time of the observation group were significantly shortened, and the daily amount of disinfection was significantly increased(P<0.01). The incidence of postoperative infection of the observation group was 3.00%(15/500), lower than 5.60% (28/500) of the control group, there was no significant difference between the two groups (P>0.05). Totally 144 strains of pathogens were isolated from the peripheral blood, urine and bile specimens of the patients with postoperative infection, 59 (40.97%) of which were gram-positive bacteria, and 85 (59.03%) were gram-negative bacteria. CONCLUSIONS O-phthalaldehyde is highly effective and safe for the disinfection of endoscopes and can reduce the incidence of postoperative infection in the ERCP patients.