Objective:This study aimed to investigate the associations between baseline peripheral blood biomarkers and outcome in patients with non-small cell lung cancer (NSCLC) receiving immune checkpoint inhibitors (ICIs). Methods: A retrospective analysis was conducted of 84 patients with stage III or IV NSCLC who received PD-1 inhibitors combined with chemotherapy as first-line treatment in the First Affiliated Hospital of Nanjing Medical University from January 2020 to September 2022. The efficacy was evaluated according to RECIST1.1 criteria and follow-up of progression-free survival (PFS). COX regression models were used to assess the univariate and multivariate survival analysis and prognostic effect of baseline peripheral blood before treatment. Kaplan-Meier methods were drawn survival curves. Log-rank tests were used to analyze the survival rates between groups. Results: The median follow-up time was 9.93（5.68~15.38） months, and the median progression-free survival (mPFS) was 9.42（5.63~12.88）months. COX univariate regression analysis and Kaplan-Meier survival curves showed that PD-L1 was an independent predictor of immune efficacy (HR = 0.299, P = 0.003)，patients with high monocyte percentage (≥8.15%) had better PFS than those with low monocyte percentage （HR=0.313，95%CI：0.137~0.711，P=0.006，mPFS 14.37 months vs 7.60 months）. Patients with high eosinophil percentage (≥1.90%) also had better PFS than those with low eosinophil percentage（HR=0.296，95%CI：0.092~0.958，P=0.042，mPFS 13.87 months vs 7.93 months）. COX multivariate regression analysis showed that both parameters were independently associated with both better PFS. However，peripheral blood lymphocyte subsets and inflammatory parameters had no predictive role for ICI efficacy. Conclusion: For patients with NSCLC, the percentage of monocytes and eosinophils may be useful predictive markers of response to chemotherapy combined with immunotherapy as first-line therapy, and higher were associated with longer progression-free survival time.