Abstract: OBJECTIVE To investigate the etiology and risk factors of nosocomial infection in patients with advanced non-small cell lung cancer (NSCLC) treated with radiofrequency ablation combined with chemotherapy. METHODS The data of 140 cases of advanced NSCLC patients received radiofrequency ablation combined with chemotherapy in our hospital from Aug.2015 to Aug.2017 were studied.The infection rate and sites of nosocomial infection of the patients during hospitalization were analyzed, the distribution of pathogens was detected, and the risk factors for infection were explored by logistic regression analysis. RESULTS A total of 32 cases of nosocomial infection occurred in the 140 cases of advanced NSCLC patients, and the infection rate was 22.86%.The infection site was mainly upper respiratory tract, accounting for 31.25%.A total of 48 strains of pathogens were isolated, among which gram-negative bacteria (30 strains) accounted for 62.50%, gram-positive bacteria (16 strains) accounted for 33.33%, and fungi (2 strains) accounted for 4.17%.The results of multivariate analysis showed that age of more than 60 years old, tumor staging of TNM, chemotherapy protocol, chemotherapy cycle, hormone use, neutrophil count, CD4/CD8 ratio were independent risk factors for nosocomial infection in patients with advanced non-small cell lung cancer during the treatment, whereas the neutrophil count and CD4 /CD8 were protective factors. CONCLUSION The nosocomial infection rate is relatively high for advanced NSCLC patients receiving radio frequency ablation combined with chemotherapy.It is of great importance to provide corresponding preventive measures based on the etiology and risk factors.