Abstract: Objective: To study the incidence of postoperative pneumonia(POP) and the distribution of multi-drug resistant bacteria(MDRO) in surgical patients, and analyze the influencing factors of POP after surgery.Methods: From January 2017 to December 2019, all surgical patients in the hospital were selected. According to the year, department and age group, the incidence of POP, the mortality rate of POP patients, the detection rate of MDRO and the detection rate of non multi-drug resistant organism, all patients were divided into different groups according to gender, age, use of preoperative immunosuppressive agents, timing of operation, use of tracheotomy, use of ventilator, underlying diseases, grade of operation, use of gastric tube, postoperative antibiotic usage and bleeding volume. The incidence rate of POP was compared in each group. When P<0.05, it was included in the multivariate Logistic regression analysis.Results: A total of 82 cases of POP occurred in 7424 patients, and the incidence rate was 1.10%. There was no significant difference in POP incidence rate in different years, POP mortality rate, MDRO detection rate and non multi-drug resistance organism detection rate(P>0.05). The incidence rate of POP among different surgical departments was statistically significant(χ²=52.280, P<0.001). The incidence of POP in groups of 50-75 years old and>75 years old was higher than that in groups of 0-25 years old and 25-50 years old, the difference was statistically significant(P<0.05). MDRO was mainly G^-, the highest proportion was Acinetobacter baumannii, followed by Pseudomonas aeruginosa. The occurrence of POP after surgery was related to the patient's age, whether to use immunosuppressive agents before surgery, whether to select surgery time, whether to have a tracheotomy, whether there was an underlying disease, the grade of surgery, and whether the use of antibiotics after surgery was reasonable(all P<0.05). Age, preoperative use of immunosuppressive agents, non-selective surgery, tracheotomy, underlying diseases, high surgical grade, and unreasonable use of antibiotics after surgery were all risk factors for POP after surgery(all P<0.05).Conclusion: Surgical POP had a high morbidity and mortality rate in our hospital, which need to be highly valued by the clinic doctors. Among the surgical patients, the third and fourth grade surgery patients with old age, underlying disease, use of immunosuppressive agents, emergency surgery, and use of tracheotomy were listed as people who need key protection, use antibiotics rationally after surgery in order to reduce the incidence of postoperative POP and MDRO.