Objective To summarize retrospectively the clinical technology of repairing osteonecrosis of femoral head (ONFH) by free vascularized fibular grafting (FVFG), and the value of modified instruments in operation. Methods Between March 2011 and January 2013, 35 patients with ONFH (47 hips) who underwent FVFG with modified instruments. There were 24 males (32 hips) and 11 females (15 hips), aged 34 years on average (range, 22-43 years). The unilateral hip was involved in 23 cases and the bilateral hips in 12 cases. The disease duration ranged from 5 to 9 months (mean, 7 months). Based on etiology, 25 hips were classified as alcohol ONFH, 12 hips as corticosteroids ONFH, 3 hips as trauma ONFH, and 7 hips as idiopathic ONFH. According to the Association Research Circulation Osseous(ARCO) stage, 3 hips were rated as stage I, 39 hips as stage II, and 5 hips as stage III on the X-ray films. The preoperative Harris score was 58.2±6.1. Results The time to get fibula was 15-35 minutes (mean, 25 minutes). The operation time was 90-200 minutes (mean, 130 minutes), and the blood loss during operation was 150-500 mL (mean, 270 mL). All the patients achieved primary healing of incision, without complication of infection or deep vein thrombosis. All 35 patients were followed up 12-42 months, with an average of 28 months. The Harris score at final follow-up was 87.3±5.7, showing significant difference when compared with preoperative score (t=102.038,P=0.000). Radiographic results at final follow-up showed good position of fibula; and necrosis was improved in 9 hips, had no changes in 36 hips, and aggravated in 2 hips. Conclusion FVFG for ONFH can improve hip function effectively, and modified instruments can improve operation efficiency.