Abstract: ob＜x＞jective To analyze the pulmonary function related indexes such as forced vital capacity (FVC), forced expiratory volume in the first second (FEV1), FEV1 / FVC and carbon monoxide diffusion function (DLCO) in patients with stage III and IV non-small cell lung cancer (NSCLC) after treatment with PD-1 inhibitor and the change of efficacy. Methods The data of NSCLC patients treated in our hospital from July 2019 to March 2021 were prospectively analyzed and taken as the research ob＜x＞ject. They were randomly divided into control group (n = 41) and observation group (n = 39). The control group was treated with AP or TP Chemotherapy, and the observation group was treated with chemotherapy combined with PD-1 inhibitor. After 4 cycles, the T lymphocyte subsets (CD3+, CD4+, CD8+) 、lung function (FVC, FEV1, FEV1 / FVC, DLCO) were detected; The data of serum cytokeratin 19 fragment (CYFRA211), squamous cell carcinoma antigen (SCCA) and carbohydrate antigen (CA125) were collected and analyzed. Results After 4 cycles of treatment, the total effective rate (ORR) of the observation group was 38.46%, which was higher than 9.76% of the control group ( P < 0.05); Pulmonary function was significantly improved (P < 0.05); Tumor markers also showed a downward trend (P < 0.05); CD3 + and CD4 + were higher than before ( P < 0.05). Conclusions Lung function (FVC, FEV1, FEV1 / FVC and DLCO), T lymphocyte subsets (CD3 +, CD4+), tumor markers (CYFRA21-1, SCCA and CA125) and efficacy of stage III and IV NSCLC after chemotherapy combined with PD-1 inhibitor are improved, and the improvement is more obvious than that of chemotherapy alone ，and can be actively used in clinical practice.