To analyze the effectiveness comparison of external fixator combined with Kirschner wire fixation and Kirschner wire fixation in the treatment of cubitus varus deformity in children. A retrospective case-control study was conducted to collect 36 children of postoperative supracondylar humerus fracture complicating cubitus varus deformity between January 2018 and July 2022. Among them, 17 cases were treated with distal humeral wedge osteotomy external fixation combined with Kirschner wire fixation (observation group), and 19 cases were treated with distal humeral wedge osteotomy and Kirschner wire fixation (control group). The baseline data including age, gender, deformity side, time from fracture to operation, carrying angle of the healthy side and preoperative carrying angle of the affected side, elbow flexion and extension range of motion, and lateral condylar prominence index (LCPI) showed no significant difference between the two groups ( P>0.05). The operation time, hospitalization cost, healing time of osteotomy, postoperative complications, and the carrying angle, LCPI, and elbow flexion and extention range of motion were recorded and compared between the two groups. The elbow function was assessed by Oppenheim score at 3 months after operation and at last follow-up. The children in both groups were followed up 13-48 months, with an average of 26.7 months. There was 1 case of needle tract infection in the observation group and 2 cases in the control group, and no nerve injury occurred, the difference in the incidence of complication (5.88% vs 10.53%) between the two groups was not significant ( χ 2=0.502, P=0.593). There was no significant difference in the operation time and fracture healing time between the two groups ( P>0.05); the hospitalization cost of the observation group was significantly higher than that of the control group ( P<0.05). The Oppenheim score of the observation group was significantly better than that of the control group at 3 months after operation ( P<0.05), but there was no significant difference in the Oppenheim score between the two groups at last follow-up ( P>0.05). At last follow-up, the carrying angle of affected side significantly improved in both groups when compared with preoperative ones ( P<0.05); the differences of the pre- and post-operative carrying angle of affected side and elbow flexion and extension range of motion showed no significant differences between the two groups ( P>0.05), but the difference in pre- and post-operative LCPI of the observation group was significantly better than that of the control group ( P<0.05). External fixator combined with Kirschner wire fixation and Kirschner wire fixation both can achieve satisfactory correction of cubitus varus deformity in children, and the former can achieve better short-term functional recovery of elbow joint and reduce the incidence of humeral lateral condyle protrusion.