Recombinant Anti-CD3 x Anti-FcRH5 Bispecific Antibody (Fab-scFv-Fc) requires expression of three polypeptide chains, encoding two heavy chains (Fc-containing chains) and one light chain, respectively. The Fab of anti-CD3 antibody variable domain is fused to the Fc-knob domain with a hinge region and the same as the scFv of anti-FcRH5 to the Fc-hole domain, or vice versa. The Fab-Fc and scFv-Fc fragments can be paired via the interaction of the Fc regions. This BsAb can retarget T cells to tumor cells. It is designed for the research of Multiple myeloma (MM); B cell malignancies therapy.