Objective To investigate the feasibility of the preservation of the epiphysis and joint function of the distal femur in children with osteosarcoma with epiphyseal distraction by external fixator. Methods Between July 2007 and May 2011, 6 children with osteoblastic osteosarcoma of the distal femur underwent epiphyseal distraction by external fixator, combined with tumor resection and repair with massive allograft bone transplantation to preserve the epiphysis and joint function of the distal femur. There were 4 boys and 2 girls, aged from 9 to 14 years (mean, 10.5 years). According to Enneking clinical staging, 4 cases were in stage II A and 2 cases in stage II B. According to San-Julian et al. typing for metaphyseal tumor invasion, 3 cases were in type I and 3 cases in type II. The size of tumor ranged from 6 cm × 4 cm to 12 cm × 9 cm. All patients received 2 cycles of COSS 86 chemotherapy before operation and 4 cycles after operation. Results Poor healing of incision was observed in 1 case because of rejection of allograft bone and good healing was obtained after the symptomatic treatment, healing of incision by first intention was achieved in the other children. All 6 cases were followed up 11 to 56 months (mean, 37.5 months). One case died of lung metastasis at 2 years after operation. X-ray films showed no complication of internal fixator loosening and broken or bone nonunion. According to the functional evaluation criteria of International Society of Limb Salvage (ISOLS) at last follow-up, the results were excellent in 3 cases, good in 2 cases, and fair in 1 case; the excellent and good rate was 83.3%. The length of operated limb was (62.97 ± 7.51) cm, showing significant difference when compared with that of normal limb [(64.03 ± 7.47) cm] (t=0.246 6, P=0.813 4). Conclusion On the premise of adaptable indication, effective chemotherapy, and thoroughly tumor resection, the epiphyseal distraction by external fixator can obtain satisfactory results in limb-length and limb function in children with osteoblastic osteosarcoma of the distal femur.