Recombinant Anti-DKK1 x Anti-SOST Bispecific Antibody (IgG(L)-scFv) is formed by an IgG and two scFv moieties. The scFv fragments from an anti-DKK1 antibody are fused to the C terminus of an anti-SOST IgG light (L) chains, or vice versa. It is a type of appended IgGs, which is bispecific and tetravalent (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.