Objective To evaluate the effect of nano-hydroxyapatit e collagen (nHAC) bone and marrow mesenchymal stem cells (MSCs) on the treatment of rabbit osteonecrosis of the femoral head (ONFH) defect. Methods From June to October 2004, animal models of ONFH defect were established i n 45 New Zealand rabbits. They were divided into 3 groups randomly:In group A, as the control group, defect was not filled with any implants; In group B with nHAC; In group C with nHAC+MSC. Imaging and histological observation were made 4, 8, 12 weeks after operation. Results group C had a better o steogenesis ability than group B and group A. group B had a better osteogenesis ability than group A. Obvious new bones and osteogenesis were observed in group C 4 weeks after operation. The defect areas in group C were almost repaired 12 weeks after operation. Conclusion nHAC has a better effect of o steoconduction and it is a superior material for repairing bone defect of ONFH a nd of great value in treating ONFH when compounded with MSCs.