The conception of molecular residual disease (MRD) extending from hematologic tumor to solid tumors. Evidences supporting MRD evaluation for lung cancer by liquid biopsy has gradually accumulated, especially circulating tumor DNA (ctDNA). In this observational study, the investigators prospectively enroll stage I-IIIA non-small cell lung cancer (NSCLC) patients who underwent complete resection. Preoperative blood sample, tumor tissue and dynamic postoperative blood samples are collected continuously for MRD detection. This study aim to explore the prognostic value of MRD for stage I-IIIA NSCLC patients after complete resection.