Objective To understand the incidence and severity of postoperative acute pain in patients undergoing day surgery, and to explore the influencing factors of moderate to severe pain after surgery, so as to provide a reference for pain management in day surgery. Methods Convenience sampling method was used to select patients undergoing day surgery under multi-modal pain management in West China Hospital of Sichuan University between April and August 2020, and the general conditions, surgical conditions, and postoperative pain of the patients were investigated. According to the degree of postoperative pain, patients were divided into mild pain group and moderate to severe pain group. Logistic regression analysis was used to explore the influencing factors of postoperative pain in the two groups. Results A total of 509 patients were finally included, of which 69 patients presented with moderate to severe pain. Logistic regression analysis showed that patient age [odds ratio (OR)=0.970, 95% confidence interval (CI) (0.946, 0.993), P=0.012], pain threshold [OR=1.348, 95%CI (1.048, 1.734), P=0.020] and postoperative drainage tube [OR=2.752, 95%CI (1.090, 6.938), P=0.017] were the influencing factors of moderate to severe pain after surgery. Conclusion Under multimodal pain management, the incidence of moderate to severe pain in day surgery patients is low, and medical staff should further strengthen pain management from the factors affecting pain to reduce the incidence of moderate to severe pain after surgery.