Abstract: OBJECTIVE To analyze the distribution of pathogens and risk factors for pulmonary infections in the patients undergoing craniocerebral surgery. METHODS A total of 302 patients who were hospitalized and received craniocerebral surgery in Nantong First People's Hospital from Feb. 2020 to Feb. 2025 were recruited as the research subjects and were divided into the pulmonary infection group with 36 cases and the non-infection group with 266 cases according to the status of pulmonary infection complication. The demographic characteristics, perioperative related factors and CD₄⁺ T lymphocyte(CD₄⁺) counts at the admission were collected from the patients. The etiological culture was carried out for the patients with pulmonary infections, the antimicrobial susceptibility testing was performed. Multivariate logistic regression analysis was performed for the risk factors for the pulmonary infections. The dose-effect relationship between the CD₄⁺ and the risk of pulmonary infections was analyzed by restricted cubic spline model. RESULTS Totally 48 strains of pathogens were isolated from the 36 patients with pulmonary infections, 31 (64.58%) of which were gram-negative bacteria; Acinetobacter baumannii (15 strains), Pseudomonas aeruginosa (10 strains) and Klebsiella pneumoniae (6 strains) were the major species. The result of multivariate logistic regression analysis showed that the no less than 65 years of age (OR=2.440), Glasgow Coma Scale (GCS) score no more than 8 points (OR=3.117) and tracheotomy(OR=4.288) were the risk factors for the pulmonary infections (all P＜0.05). The restricted cubic spline model indicated that there was an approximately "n" -shaped nonlinear relationship between the CD₄⁺ at the admission and the risk of pulmonary infections(P＜0.001). CONCLUSIONS The gram-negative bacilli are dominant among the pathogens causing the postoperative pulmonary infections in the patients undergoing craniocerebral surgery, and the isolation rates of MDROs causing the pulmonary infections are high. There is a nonlinear relationship between the CD₄⁺ at the admission and the risk of infections.