Recombinant Anti-CD3 x Anti-FcRH5 Bispecific Antibody (IgG-Fv) is formed by an Immunoglobulin G (IgG) and a fragment variable Fv region, in which the Fc of IgG is engineered by KIH. The Fv region of an anti-CD3 antibody variable domain is fused to the C terminal of an IgG of anti-FcRH5 antibody, or vice versa. The format retains desired characteristics of intact antibodies. This BsAb can retarget T cells to tumor cells. It is designed for the research of Multiple myeloma (MM); B cell malignancies therapy.