ObjectiveTo explore the effect of metabolic syndrome (MS) on postoperative pulmonary infection in patients with colorectal cancer (CRC) and to construct a risk prediction model for postoperative pulmonary infection in CRC patients. MethodsRetrospective collection of clinical data from 291 CRC patients who underwent surgical treatment at Suzhou Ninth Affiliated Hospital of Soochow University from January 2020 to August 2024. To explore the risk factors of postoperative pulmonary infection in patients with CRC and to establish a nomogram model. ResultsAmong the 291 CRC patients enrolled, there were 58 MS patients (19.93%) and 233 non-MS patients (80.07%). Compared with patients without MS, CRC patients with MS had longer surgery time and higher incidence of postoperative pulmonary infection (P<0.05). The results of multiple logistic regression analysis showed that smoking history, body mass index (BMI)≥25 kg/m2, MS, increased surgical time and increased intraoperative bleeding were all risk factors for postoperative pulmonary infection in CRC patients (P<0.05). Based on these risk factors, a nomogram model was constructed. The area under the receiver operating characteristic curve was 0.845 [95%CI (0.769, 0.906)], and the sensitivity and specificity were 84.2% and 87.5% respectively. The internal verification of Bootstrap test showed that the simulated curve and the actual curve had good consistency. The clinical decision curve analysis shows that when the threshold probability is in the range of 8–84%, the net benefit of the model for patient diagnosis is higher. ConclusionsMS increases the risk of postoperative pulmonary infection in CRC patients. At the same time, smoking history, high BMI, long operation time, and more intraoperative blood loss are also risk factors for postoperative pulmonary infection in patients with CRC. Building a model based on this can effectively evaluate the risk of postoperative pulmonary infection in CRC patients.