Objective：To explore the effect of high-fat diet on delayed pleural effusion after single-port video-assisted thoracoscopic lung surgery. Methods：A retrospective analysis was conducted on the clinical data of 571 patients who underwent single-port video- assisted thoracoscopic lung surgery at the Department of Thoracic Surgery，Nanjing Medical University Affiliated Brain Hospital from December 2021 to June 2023. Patients were divided into a high - fat diet group and a non - high - fat diet（control）group based on postoperative dietary habits. Propensity score matching analysis was used to match the two groups of patients with a ratio of 1∶1，and then the incidence of delayed pleural effusion and other postoperative complications was compared between the matched groups. Results：Before matching，the high-fat diet group included 166 patients，with 45 males and 121 females，and an age of 56.0（49.0， 66.0）years. The control group included 405 patients，with 164 males and 241 females，and an age of 57.0（48.0，67.0）years. After propensity score matching，each group included 130 patients. The high-fat diet group showed significantly higher incidences of delayed pleural effusion（OR=1.080，95%CI：1.013-1.152，P=0.019），postoperative cough（OR=1.203，95% CI：1.091-1.326，P=0.001），and postoperative chest tightness（OR=1.166，95%CI：1.038-1.311，P=0.010） compared to the control group，with statistically significant differences. Conclusion：A high-fat diet after single-port thoracoscopic lung surgery can significantly increase the incidence of delayed pleural effusion.