Objective To analyze the influencing factors for surgical site infection (SSI) after gastrointestinal perforation repair surgery by decision tree and logistic regression model. Methods Patients who underwent gastrointestinal perforation repair surgery at a hospital of Mianyang City from January 2018 to January 2023 were selected as the research subjects. Clinical data of the patients were collected. Patients were divided into the SSI (+) group (n=41) and the SSI (-) group (n=322) based on whether SSI occurred after surgery. Influencing factors for SSI after gastrointestinal perforation repair surgery were analyzed by univariate and multivariate logistic regression. Re-levant decision tree prediction model was constructed. Results Among the 363 patients who underwent gastrointestinal perforation repair surgery, 41 developed postoperative SSI, with an incidence of 11.29%. Univariate analysis results showed that there were statistically significant differences between two groups of patients in body mass index (BMI), albumin level, preoperative antimicrobial use, duration of preoperative abdominal pain, and duration of surgery (all P < 0.05). Multivariate logistic regression analysis showed that higher BMI (OR=2.059, 95%CI: 1.103-3.842), albumin levels < 35 g/L (OR=2.761, 95%CI: 1.312-5.811), duration of preoperative abdominal pain ≥24 hours (OR=3.589, 95%CI: 1.659-7.763), and duration of surgery ≥2 hours (OR=3.314, 95%CI: 1.477-7.435) were independent risk factors for postoperative SSI in patients after gastrointestinal perforation repair surgery (P < 0.05), while preoperative antimicrobial use was a protective factor (OR=0.338, 95%CI: 0.166-0.690, P < 0.05). The decision tree model based on the above factors was constructed to predict the risk of SSI in patients after gastrointestinal perforation repair surgery. Validation of the model showed that the area under the receiver operating characteristic (ROC) curve (AUC) was 0.811 (95%CI: 0.794-0.825). Conclusion The risk factors for postoperative SSI in patients after gastrointestinal perforation repair surgery include high BMI, albumin level < 35 g/L, duration of preoperative abdominal pain ≥24 hours, and duration of surgery ≥2 hours. The protective factor is antimicrobial use before surgery. The decision tree model constructed based on the influencing factors has good predictive ability for the risk of postoperative SSI in patients after gastrointestinal perforation repair surgery.