Objective To investigate the feasibility and clinical efficacy of free graft of vascularized iliac bone flap based on deep iliac circumflex vessels for the treatment of osteonecrosis of femoral head (ONFH). Methods Twelve cases of ONFH (13 hips) received free graft of vascularized iliac bone flap based on deep iliac circumflex vessels from April, 2016 to July, 2017. The average Harris score was (74.7±6.9) in the second stage and (68.6±9.2) in the third stage. After debriding the necrosis bone of the femoral head, the contralateral vascularized iliac bone flap had been harvested, and then implanted into the femoral head. The deep iliac circumflex artery and its accompanying vein were anastomosed with the transverse branch (or ascending branch) of the lateral circumflex femoral artery and concomitant vein respectively. The herringbone brace was used for hip fixation for 3 weeks after operation. X-ray examination(1, 3, 6, 9 and 12 months after operation, respectively) and Harris hip score (6 and 12 months after operation, respectively) were performed to evaluate the recovery results of the femoral head. Scores were recorded and analyzed by paired t-test. The difference was considered to statistically significant if P<0.05. Results The patients were followed-up for 15 (12-20) months. The iliac bone flap of 12 patients (13 hips) healed well. There was no necrosis and collapse in 12 hips, except 1 femoral head collapsed slightly because of weight loading too early. The average Harris score was (91.6±4.5) of the second stage and (84.8±6.1) of the third stage. Compared with scores before the operation, the difference was statistically significant (P<0.05). Conclusion Free vascularized iliac bone grafting based on deep iliac circumflex vessels is an ideal treatment for ONFH head in middle and advanced stage. Key words: Osteonecrosis of the femoral head; Iliac bone flap; Deep iliac circumflex vessels; Transplantation; Harris hip score