Objective: To explore repair effects of  injectable nano-hydroxyapatite/ chitosan（nHA/CS） composite on radius bone defect. Methods: Bone defect with the length of 10 mm were created on the middle of each radius of 18 New Zealand white rabbits. the defects was filled with the nHA/CS composite as treatment group, while the others were filled with hydroxyapatite（HA） as control. The ability of repairing bone defect was evaluated by gross observation, X-ray, histopathological and SEM 4, 8, 12 weeks after operation. Results: ① The gross and X-ray showed that, in treatment group, the callus grew well and bone defect was repaired completely, oppositely, in control group, bone defect was repaired partly, with some nonunion. ② Histomorphology showed that, the new formed bone in treatment group was confirmed integral and the medullary cavity recanalized after 12 weeks, however, a little of  new  bone formed in the control group, accompanied with connective tissues growing into the defects. ③ Under the SEM, materials was replaced by newly formed bone after 12 weeks in treatment group. Conclusions: The nHA/CS has better ability of bone repairing than that of the HA.