Abstract: The cod bone collagen hydrolysates were prepared by commercial protease. Utilizing cultured MG-63 cells, the osteogenic effect of collagen hydrolysates with different molecular weights was studied in vitro.Compositional analyses and histological observation was performed. Cod bone collagen hydrolysates with different molecular weights were obtained. The cultured MG-63 cells were used to investigate the osteogenic effect by detecting the ALP activity and the m RNA expression of Bone morphogenetic protein( BMP- 2),Osteoprotegerin(OPG) and Receptor activator of nuclear factor-κB ligand(RANKL. The proximate analysis of fish bone exhibited that protein content in bone reached 14.5%. Large amounts of collagen fibrils in fish bone were observed using Van Gieson staining technology. Cod bone collagen hydrolysates could increase the ALP activity and BMP-2 m RNA expression level,meanwhile remarkably increase the ratio of OPG/RANKL m RNA expression in order to indirectly influence the osteoclast differentiation and maturation. Cod bone was a good collagen resource,the collagen hydrolysates extracted from cod bone exhibited osteogenic effect and could be used as a natural anti-osteoporotic supplement.