Bone morphogenetic protein (BMP) homodimers are of significant osteoinductivity. However, their clinical application is limited because of high effective dosage. Recently, BMP heterodimers are reported to address the issue. This is a review of the researches on BMP heterodimers, including existent evidences, types and synthetic methods, biological activities in comparison to BMP homodimers and possible mechanisms, further research direction and future expectations.