Objective:To investigate the efficacy of thoracoscopic segmentectomy of the dominant lung segment versus thoracoscopic segmentectomy of the complex lung segment for the treatment of stage I non-small cell lung cancer (NSCLC). Methods:This is a case-control study. The clinical data of 110 patients with stage I NSCLC who received treatment in Jinhua Municipal Central Hospital from August 2019 to August 2021 were retrospectively analyzed. These patients were assigned to a control group (thoracoscopic segmentectomy of dominant lung segment, n = 58) and an observation group (thoracoscopic segmentectomy of complex lung segment n = 52) according to the surgical method. Tumor location and resection scope in each group were recorded. Perioperative indexes, lung function indexes, complications, and short-term recurrence rates were compared between the two groups. Results:The operative time in the observation group was (175.45 ± 30.72) minutes, which was significantly longer than (152.41 ± 29.83) minutes in the control group ( t = 3.99, P < 0.05). The number of nail bins in the observation group was (4.55 ± 1.23), which was significantly greater than (3.77 ± 1.16) in the control group ( t = 3.42, P < 0.05). There were no significant differences in intraoperative bleeding volume, the number of dissected lymph nodes, postoperative drainage volume, postoperative extubation time, and postoperative hospital stay between the two groups (all P > 0.05). Forced vital capacity, forced expiratory volume in the first second (FEV 1), and FEV l/FVC ratio in the observation group were (3.89 ± 0.47) L, (2.92 ± 0.36) L, and (75.06 ± 2.47)%, which were significantly higher than (3.64 ± 0.49) L, (2.68 ± 0.35) L, and (73.63 ± 2.38)% in the control group (all P < 0.05). There was a significant difference in the incidence of complications between the observation and control groups [32.69% (17/52) vs. 20.69% (12/58), P > 0.05]. There was no significant difference in recurrence of stage I NSCLC between the observation and control groups [3.85% (2/52) vs. 1.72% (1/58), P = 0.495]. Conclusion:The overall effect and safety of thoracoscopic segmentectomy of complex lung segment in the treatment of stage I NSCLC are comparable to those of thoracoscopic segmentectomy of the dominant lung segment. However, thoracoscopic segmentectomy of complex lung segments can reduce the impact on lung function and protect lung function to the maximum extent.