Neoadjuvant immunotherapy has become the standard perioperative treatment in lung cancer, but its effective predictive biomarkers are lacking. A small cohort reported that homologous recombination deficiency (HRD) can be used as a reliable biomarker to predict the efficacy of neoadjuvant immunotherapy, but the findings need to be validated in larger cohorts. Moreover, circulating tumor DNA (ctDNA) has the potential to predict the therapeutic efficacy of neoadjuvant immunotherapy. This study intends to prospectively collect patients with driver-negative stage II-IIIB NSCLC who are scheduled to receive neoadjuvant immunotherapy and surgical resection and verify the value of HRD in predicting the efficacy of neoadjuvant immunotherapy. Meanwhile, the blood samples before and after neoadjuvant immunotherapy were collected for high-depth ctDNA detection to explore the correlation between the dynamic changes of ctDNA and the efficacy and prognosis of neoadjuvant immunotherapy.