AIM: To investigate the relationship between the dynamic changes of Lymphocyte-to-monocytes ratios (LMR) before PD-1 inhibitor treatment and the efficacy and prognosis of PD-1 inhibitor treatment in patients with advanced non-small cell lung cancer (NSCLC). METHODS: The clinical case data of 83 patients with advanced non-small cell lung cancer admitted to the Cancer Hospital of Wuhu Second People's Hospital from June 2019 to July 2022 were retrospectively analyzed. The routine blood LMR values of all patients before and after treatment were collected, the cut-off value was calculated according to the ROC curve, and the LMR was divided into two groups: high and low before treatment and after treatment. The differences of ORR, DCR, PFS and OS among the patients in each group were analyzed and compared, and the value of LMR value and dynamic changes after treatment on the efficacy and prognosis of patients with PD-1 inhibitors in the treatment of NSCLC patients was analyzed. RESULTS: According to the ROC curve, the critical value of LMR was 1.8, and the LMR was divided into the low LMR group at baseline (LMRB/S<1.8)，the high LMR group at baseline (LMRB/S≥1.8) and the low LMR group after treatment (LMRafter<1.8) and the high LMR group after treatment (LMRafter≥1.8). The ORR and DCR after immunotherapy in the high LMRB/S group were higher than those in the low LMRB/S group (P=0.037; P=0.002 5). Among the patients with low LMRB/S before treatment, the DCR of the LMRafter≥1.8 group was better than that of the LMRafter<1.8 group after treatment (P=0.005). Among the patients with high LMR before treatment, the DCR of the LMRafter≥1.8 group was better than that of the LMRafter<1.8 group (P=0.034). Kaplan-Meier analysis showed that PFS and OS were longer in the high LMRB/S group than in the low LMRB/S group before treatment. In the low LMRB/S group before treatment, PFS and OS were longer in patients with LMRafter≥1.8 than those with LMRafter<1.8 (P=0.047; P=0.007). Multivariate Cox regression model analysis showed that high LMRB/S value before treatment was an independent risk factor for PFS and OS in NSCLC patients (P=0.006; P=0.033). CONCLUSION: High LMR value of patients before immunotherapy may improve the efficacy of PD-1 inhibitors, improve the prognosis of patients, and prolong the survival time. Moreover, the increase of LMR value after treatment may increase the efficacy of patients with low LMR before treatment and improve the prognosis of patients.