Objective To analyze the effectiveness and application value of epiphysis preserving by the method of physeal distraction for treatment of femur osteosarcoma in children’s limb saving surgery. Methods Between January 2007 and January 2011, 6 patients with femur osteosarcoma underwent epiphysis preserving operation by physeal distraction. There were 4 males and 2 females with a mean age of 11.4 years (range, 9-14 years). The mean disease duration was 4.8 months (range, 1-9 months). The pathology confirmed osteosarcoma in all patients by core needle or open biopsy, including 1 case of osteogenic sarcoma, 1 case of chondroblastic osteogenic sarcoma, 1 case of osteoblastic osteogenic sarcoma, and 3 cases of no classified osteosarcoma. The clinical stage was IIA in 1 case and IIB in 5 cases according to the Enneking staging system. All patients received 2 cycles of neoadjuvant chemotherapy before operation. Then physeal distraction was performed for 4-7 days (mean, 5.7 days) based on Cantilde;adell technique. After 1-2 days of physeal distraction, massive allograft bones and interlocking intramedullary nails were used to reconstruct bone defect after tumor resection. All patients received another 4-6 cycles of chemotherapy and were followed up. Bone healing, limb discrepancy, and complications were recorded. Functional outcomes were assessed by the system of the Musculoskeletal Tumor Society (MSTS) and the range of motion (ROM) of both knee joints. Results Superficial infection occurred in 1 case and was cured after dressing change, and primary healing was obtained in the other patients. All 6 patients were followed up 2.5 years on average (range, 1-5 years). Symptoms of pain and swelling disappeared. No complication of allograft rejection, loosening or breaking of fixation occurred. No relapse or metastasis happened during follow-up. Bone healing was observed at the metaphysis junction in 5 cases at 6-9 months after operation and in 1 case at 14 months. Delayed union happened at the diaphysis junction in all patients. Different amount of callus formation was seen at the surface of diaphysis junction, but the fracture line remained clear at 12-48 months after operation. At last follow-up, limb discrepancy was 1-3 cm in 4 patients and 3-5 cm in 2 patients; 3 patients had compensatory scoliosis, and 2 patients had claudication. The MSTS score was 27.20 ± 1.92, showing significant difference (t= — 4.12, P=0.00) when compared with preoperative score (19.60 ± 2.74). The ROM of affected knee was (127.00 ± 17.89)°, showing no significant differences when compared with preoperative ROM (109.00 ± 12.45)° (t= — 1.84, P=0.10) and with ROM of normal knee (126.00 ± 9.62)° (t= — 0.11, P=0.92). Conclusion Limb saving surgery by physeal distraction can be used in young patients with open epiphyseal plate, which has the advantages of simple operation, good effectiveness, and less complications.