Abstract: Bone morphogenetic proteins 9 belongs to the bone morphogenetic protein family (BMPs), which mediate the osteogenic differentiation of mesenchymal stem cells, muscle cells and preosteoblasts, and promote chondrogenesis. The mechanism of osteogenic differentiation induced by BMP-9 is not identical to that of traditional bone morphogenetic proteins (BMP-2, 4, 7, etc.). The ability of BMP-9 to induce osteogenic differentiation of MSCS was significantly stronger than other BMPs (such as BMP-2, 4, 7, etc.). The traditional BMP inhibitor Noggin has no significant inhibitory effect on the ability of BMP-9 to promote bone differentiation.In this review, the structure and receptor of BMP-9, the function and signaling mechanism of osteogenic differentiation, and chondrogenic differentiation are reviewed, and the development prospect of BMP-9 is prospected.