Recombinant Anti-DKK1 x Anti-SOST Bispecific Antibody (scFv-IgG) is formed by an IgG and two scFv fragments. The scFvs from an anti-DKK1 antibody variable domain are respectively connected to the N terminus of the anti-SOST IgG heavy chains or light chains to form scFv-(H)IgG or scFv-(L)IgG. It is a type of appended IgGs and has 2+2 antigen-binding valency. 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.