Recombinant Anti-HER2 x Anti-HER3 Bispecific Antibody (Miniantibody) is a fusion protein of two scFv fragments combined with distinct specificity. One scFv of an anti-HER2 antibody variable domain is linked to another scFv of an anti-HER3 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 and inactivate two receptors simultaneously. It is designed for the research of Breast cancer; Gastric cancer; Prostate cacncer; Ovarian cancer; Solid tumors therapy.