Objective To evaluate the effect of porous gradient composites with hydroxyapatite(HA)/zirconia(ZrO₂) in repair of lumbar vertebra body defects of dogs.Methods(1) New porous gradient HA/ZrO₂ bio-composites were prepared using Foam impregnation, gradient compound and high temperature sintering;(2) A total of 18 adult Beagle dogs, weighted 10~13 kg and aged 5~8 months, were assigned randomly into two subgroups and were implanted with new porous gradient HA/ZrO₂ bio-composites(subgroup A in 12) and autologous iliac bone(subgroup B in 6);(3) The relative data was analyzed on roentgenoscopy, mophology and biomechanics of post-operation. The effect was compared between the subgroup A and the subgroup Bto repair the vertebral body defect.Results The porocity of new porous gradient HA/ZrO₂ bio-composites is 25 ppi(pores per inch), and the pores are well distributed with diameter of 100~300μm. The roentgenoscopy of post-operation displayed that new-bone formation is increased gradually, and the interface between bio-composite and host-bone becomes blur, and the new-bone around the bio-composite integrated into host-bone at 24 weeks of post-operation in subgroup A. As to subgroup B, the resorption and restructure were found at 6 weeks after the surgery, and the graft-bone and host-bone have integrated completely without obvious boundary at 24 weeks of post-operation. Histomorphology study showed that the amount of bone within pores of the scaffold material increased with a prolonged postoperative, and that partial bio-composite was degradated and replaced by new host-bone. There was no significant difference between the two subgroups(P>0.05) in the maximum compressive strengths of biomachanics test.Conclusions New porous gradient HA/ZrO₂ bio-composites can induce bone tissue to grow into the pores, and promote the repair of cancellous bone defect, which may be applied widely to the treatment of cancellous bone defect in the future.