Abstract:[Objective] To explore the dose-effect relationship of recombinant human morphogenetic protein-2 (rhBMP-2) in the criti- cal radius bone defect model in rabbit. [Methods] A total of 36 New Zealand white rabbits were randomly divided into blank group, sponge blank group, bone autograft group, low-dose group (0.25 mg rhBMP-2), medium-dose group (0.5 mg rhBMP-2) and high-dose group (2.5 mg rhBMP-2), with 6 rabbits in each group. After a 15 mm radius bone defect was made in rabbit, the corresponding bone defect treatments were conducted respectively. The X-ray check, Micro CT examination and histological observation were performed at 4 and 8 weeks postop- eratively. [Results] Compared with those 4 weeks after surgery, Lane Sandhu X-ray scores increased in all groups at 8 weeks, which were not significantly different between the two time points in the blank group and sponge blank group (P<0.05), while statistically significantly different in the bone autograft group, low, medium and high dose groups (P<0.05). At the corresponding time points, Lane Sandhu X-ray scores ranked from low to high all as: blank groupP<0.05).Regarding Micro CT assay, the bone mineral density (BMD)and trabecular number (Tb.N) increased in all the 6grorps at 8 weeks comparde with those at 4 weeks after surgery, which proved statistically singnificant between the two time points in the low-dose,medium-dose and high-dose grouups(P<0.05).At the corresponding time points,BMD and Tb.N ranked from low to high as:low dose groupP<0.05).In addition, the histological observation showde that the maturty of new bone was dose-dependent with rhBMP-2.[Conclusion] In the dose range of 0.25mg to 2.5mg, the bone repair outcome of rhBMP-2 in the critical radial bone defect is dose-dependent.