Objective To observe the effect of parenteral nutrition on postoperative non-small cell lung cancer （NSCLC） patients treated by gemcitabine combined with nedaplatin chemotherapy. Methods Based on the prospective cohort study，258 patients with NSCLC who underwent minimally invasive surgical resection and received standard chemotherapy after surgery from July 2017 to October 2019 were selected as research objects，and they were divided into the treatment group （n = 63） and the control group （n = 195）. The control group only received enteral nutrition，while the treatment group was added parenteral nutrition. Nutritional status，immune function，lung function and incidence of adverse reactions were compared between the two groups after chemotherapy. Logistic regression was used to analyze the relationship between parenteral nutrition therapy and its related factors and postoperative complications of lung cancer. Results 53 patients were selected from the control group （195 cases），and 53 patients were selected from the treatment group （63 cases） by the method of propensity score matching. The values of anthropometric parameters （BMI） and nutritional parameters （HB，TP，ALB，PA） of the treatment group after chemotherapy were higher than those of the control group，and the differences were statistically significant （P < 0.05）. The values of immune function parameters （CD4+，CD4+/CD8+，IgG，IgA，IgM） and the lung function parameters （FVC，FEV1） of the treatment group were higher than those of the control group，and the differences were statistically significant （P < 0.05）. Logistic regression analysis showed that CD4+，IgG and FVC were the protective factors of postoperative complications of lung cancer. Conclusion Parenteral nutrition support treatment should be given to NSCLC patients treated with postoperative chemotherapy，for it could improve the nutritional status，enhance the immunity function，improve the lung function and reduce the postoperative complications.