Background and Aims Unplanned reoperation is a critical indicator for evaluating the quality of surgical treatment and prognosis in patients with gastrointestinal perforation. Identifying its underlying causes, recognizing relevant risk factors, and developing effective preventive strategies are essential for optimizing treatment outcomes and improving patient prognosis. This study aimed to investigate the causes and risk factors of unplanned reoperation following surgery for gastrointestinal perforation, in order to provide clinical guidance for targeted interventions.Methods The clinical data of 303 patients who underwent surgery for gastrointestinal perforation at the Department of General Surgery, Shijiazhuang People's Hospital, from January 2020 to July 2023, were retrospectively analyzed. Among them, 218 were males and 85 were females, with a mean age of (61.05±17.95) years. Seventeen patients experienced unplanned reoperations after operation, while 286 did not. Univariate analysis and multivariate Logistic regression were performed to identify the risk factors associated with unplanned reoperation. A predictive model was developed and its performance was assessed using the receiver operating characteristic (ROC) curve.Results Among the 17 patients who underwent unplanned reoperation, 14 were males and 3 were females, with a mean age of (65.76±15.11) years. The primary causes of reoperation included postoperative fistula (7 cases), postoperative bleeding (4 cases), surgical site infection (2 cases), wound dehiscence (2 cases), and stoma-related complications (2 cases). Univariate analysis indicated that gender, comorbidities, hypoproteinemia, history of abdominal surgery, ASA score, surgical grade, and disease duration were significantly associated with unplanned reoperation (all P<0.05). Multivariate Logistic regression revealed that male gender (OR=99.62, 95% CI=4.90-2 025.29, P<0.05), hypoproteinemia (OR=8.59, 95% CI=1.81-40.91, P<0.05), history of abdominal surgery (OR=17.28, 95% CI=3.42-87.32, P<0.05), higher ASA score (OR=11.89, 95% CI=2.73-51.72, P<0.05), higher surgical grade (OR=17.15, 95% CI=2.47-118.93, P<0.05), and longer disease duration (OR=1.04, 95% CI=1.02-1.07, P<0.05) were independent risk factors. The ROC curve analysis showed that the predictive model constructed based on the above factors had a sensitivity of 0.90, a specificity of 0.88, and an area under the curve of 0.94 (95% CI=0.88-0.99, P<0.001).Conclusion The leading causes of unplanned reoperation after gastrointestinal perforation surgery are postoperative fistula and bleeding. Male gender, hypoproteinemia, and other high-risk factors significantly increase the likelihood of reoperation. Although most such surgeries are performed emergently, comprehensive preoperative assessment of relevant risk factors is crucial to reduce the incidence of unplanned reoperation, and improve patient outcomes.