Background: Immune checkpoint inhibitors (ICIs) dramatically improved clinical outcomes of patients with resectable non-small cell lung cancer (NSCLC). However, ICIs are not the scenario of “One-size fits to all”. It is of great importance to explore biomarkers, especially via liquid biopsy-based approach, to predict or monitor treatment response. Besides comprehensive genomic profiling of primary tumor tissue, this study focused on gene expression profile of PBMCs at baseline as well as one week post 1^st immunotherapy administration, and its association with major pathological response (MPR) of neoadjuvant chem-immunotherapy in resectable NSCLC patients. Methods: Pre-treatment tumor biopsies and PBMC at baseline (D0) and 7 days after neoadjuvant chem-immunotherapy (D7) were collected from 27 patients with stage IB-IIIB NSCLC from two prospective clinical trials (NCT04422392 and NCT04762030) between Aug 2019 and July 2021. Tumor biopsies were subjected for comprehensive genomic profiling by an NGS panel covering 571 cancer related genes, and RNA from PBMC was subjected to an RNA sequencing panel covering transcripts of 2660 genes. (Amoy Diagnostics, Xiamen, China). Single sample gene set enrichment analysis (ssGSEA) was used to assess enrichment of inflammatory-related gene sets. CIBERSORT and in-housed established DAISM-DNN algorithm were applied to estimate immune cell populations from PBMC-derived gene expression profile. Results: Patients received chemo-immunotherapy achieved 59.3% of MPR. Stronger signatures including effector T cell and IFN-γ/Effector T-cell were significantly enriched in baseline PBMC samples in MPR patients (p = 0.028, p = 0.042 respectively). In parallel, significant increasing Naïve CD8 positive T cells was observed in PBMC at D7 in MPR patients by both CIBERSORT (p = 0.047) and DAISM-DNN algorithm (p = 0.018). Interestingly, at D7, signature of M0 macrophage was enriched in PBMC from patients with non-MPR. In addition, comprehensive genomic profiling indicated a numerically higher level of tumor mutation burden (TMB) in pretreatment tumor samples in MPR patients (Median TMB, MPR 11.51 mut/Mb vs Non-MPR 7.19 mut/Mb, p = 0.074). Conclusions: Expression profile of baseline PBMC as well as dynamics of PBMC profile in a short period (7 days) may predict the clinical efficacy of neoadjuvant chemo-immunotherapy. More patients are being enrolled into this study. Moreover, to validate these findings, large-scale and prospective investigations are warranted. Clinical trial information: NCT04422392 and NCT04762030.