Recombinant Anti-HER2 x Anti-HER3 Bispecific Antibody (VHH-IgG) is formed by an IgG and two VHH fragments. The VHHs from an anti-HER3 antibody variable domain are respectively connected to the N terminus of the anti-HER2 IgG heavy chains or light chains to form VHH-(H)IgG or VHH-(L)IgG. It is a type of appended IgGs and has 2+2 antigen-binding valency. 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.