Objective To observe the clinical effect of closed reduction and internal fixation on Gartland II supracondylar fracture of humerus.Methods Eighty cases of Gartland II supracondylar humerus fracture were divided into two groups according to different treatment methods: an observation group (40 cases) receiving closed reduction and internal fixation and a control group (40 cases) receiving open reduction and internal fixation. Clinical effects were compared between the two groups. The excellent-and-good rate of treatment was evaluated by Flynn elbow function evaluation criteria.Elbow function flexion and extension activity and complications were compared between the two groups.Results In the observation group, 31 cases (77.5%) were excellent, 4 cases (10.0%) were good, 4 cases (10.0%) were fair, and 1 case (2.5%) was bad by Flynn elbow function evaluation criteria, and the excellent-and-good rate of treatment was 87.5%. In the control group, 32 cases (80.0%) were excellent, 5 cases (12.5%) were good, and 3 cases (7.5%) were fair, and the excellent-and-good rate of treatment was 92.5%. The the excellent-and-good rate of treatment in observation group was lower but not significantly than that in the control group (χ²=0.1389, P=0.7094). Elbow function flexion and extension activity and carrying angle were not significantly different betweent the two groups (P>0.05).The incidence rate of complications in the control group was slightly higher than that in the observation group, but there was no significant difference (P>0.05).Conclusion Closed reduction and internal fixation of Gartland II supracondylar humerus fracture shows good clinical effects with less complications, infections, and scars, deserving further promotion.