Inclusion Criteria:  Patient age 20-79 years old. Tumor size ≤ 2 cm; Solitary tumor and located in the outer third of the lung field; Preoperative CT indicated that the nodules were non-pure glass nodules (CTR ≥ 0.25); Intraoperative frozen section confirmed invasive lung adenocarcinoma and with micropapillary patterns negative; Confirmation of R0 status by intraoperative frozen section analysis; Pulmonary function could withstand both segmentectomy and lobectomy (FEV1 > 70%); Sufficient organ function; Performance status of 0,1 or 2； Written informed consent.  Exclusion Criteria:  Patients suspected of lymph node positive by preoperative examination, including CT scans and mediastinal lymph node biopsy. Evidence revealed locally advanced or metastatic disease. Intraoperative exploration revealed accidental pleural dissemination. Patients with severe damage to heart, liver and kidney function (grade 3 ~ 4, ALT and/or AST over 3 times the normal upper limit, Cr over the normal upper limit). Patients concomitant with other malignant tumors； Women during pregnancy or breast-feeding； Systemic steroidal medication Patients had prior chemotherapy or radiation therapy for this malignancy. History of severe heart disease, heart failure, myocardial infarction within the past 6 months. Participated in other relevant clinical trial within three months