Objective To explore the factors associated with the occurrence of unplanned reoperations. Methods Surgical cases at Peking University Shenzhen Hospital from 2015 to 2023 were collected. After excluding unplanned reoperations, according to whether unplanned reoperation occurs, the included surgeries would be divided into the generate unplanned reoperation group and the non-generate unplanned reoperation group. Based on gender and age, the included surgery was matched with a propensity score of 1∶4 ratio. A logistic multiple regression model was established to investigate the influencing factors of unplanned reoperations. Results A total of 4 485 surgeries were included. Among them, there were 891 cases in the generate unplanned reoperation group and 3 594 cases in the non-generate unplanned reoperation group. The logistic regression analysis of the influencing factors of unplanned reoperation showed that different surgical levels, American Society of Anesthesiologists grades, surgical types, anesthesia methods, surgical time, and whether the unplanned reoperation discussion system can all affect unplanned reoperation (P<0.05). Conclusions The surgical level, American Society of Anesthesiologists grades, surgical types, anesthesia methods, surgical time, and whether the unplanned reoperation discussion system are influencing factors for the occurrence of unplanned reoperation. The occurrence of unplanned reoperation involves multiple levels of both the medical side and the patient side. It is necessary to formulate patient classification and early warning management and procedural prevention of unplanned reoperation based on each factor to ensure patient safety.