Objective To study the clinical effects of open reduction internal fixation on treatment of and closed reduction internal fixation of lateral condyle fractures of the humerus in children. Methods We prospectively studied 42 patients. According to appearance of the fracture line on X-rays ,there were 37 cases of type II and 5 cases of type 1 according to Milch classification system. In 22 fractures, we performed open reduction and percutaneous pin fixation; in 20, we used closed reduction and percutaneous pin fixation. Results According to the criteria of Hardare et al, clinical outcomes in the group with open reduction and percutaneous pin fixation were excellent in 20 patients, good in two patients and poor in none. Clinical outcomes in the group with closed reduction and percutaneous pin fixation were excellent in 12 patients, good in eight patients and poor in none. The difference in clinical outcome between the two groups was statistically significant (P<0.05). Two (9.1%) patient with open reduction and five (25%) patients with closed reduction had an increasing of 10? in their carrying angles, compared with the other side (P<0.05). One (4.5%) patient with open reduction and six (30%) patients with closed reduction had a lack of 10皁f extension of the elbow,compared with the other side. There was a statistically significant difference between the two groups in the lack of 10? of extension of the elbow (P<0.05). Lateral condylar carina deformity occurred in 3 (13.5%) patients with open reduction and 9 (45%) patients with closed reduction. The difference in lateral condylar carina deformity between the two groups was statistically significant (P<0.05). Conclusions Open reduction internal fixation is more effective than closed reduction internal fixation of lateral condyle fractures of the humerus in children, and there are few complications in open reduction internal fixation.