Recombinant Anti-DKK1 x Anti-SOST Bispecific Antibody (scFv-CH3) contains two chains. The anti-DKK1 scFv is fused to the Knob-CH3 domain via a hinge region and the same as the anti-SOST scFv to the Hole-CH3 domain, or vice versa. The KIH CH3 domains can facilitate to form a heterodimer and this bivalent binding leads to improvement in avidity. This BsAb can bind two factors simultaneously and promote osteoblastogenesis. It is designed for the research of Osteoporosis; Osteogenesis imperfecta (OI); Low bone mineral density; Fracture therapy.