• Patient aged 18-75 years old;

• 6 mm ≤ tumor size ≤ 20 mm;

• 0.25 \< CTR \< 1;

• Center of tumor located in the middle third of the lung field;

• ECOG score of 0,1 or 2;

• Lung function (FEV1 ≥ 1 L and ≥ 70%);

• Both lung segmentectomy and lobectomy could achieve R0 resection;

• No serious cardiopulmonary complications, and could withstand both lung segmentectomy and lobectomy;

• No hilus pulmonis and mediastinal lymph node metastasis and no distant metastasis;

⁃ Single tumor nodule or the concomitant nodule \< microinvasive tumor;

⁃ Written informed consent.