Recombinant Anti-DKK1 x Anti-SOST Bispecific Antibody (Miniantibody) is a fusion protein of two scFv fragments combined with distinct specificity. One scFv of an anti-DKK1 antibody variable domain is linked to another scFv of an anti-SOST antibody variable domain by a flexible hinge region. This BsAb format has the decreased size and better penetration than conventional IgGs in the clinical diagnostics and potentially therapy. 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.