Recombinant Anti-CEA x Anti-TNFα Bispecific Antibody (Fab-VHH-Fc) requires expression of three polypeptide chains, encoding two heavy chains (Fc-containing chains) and one light chain, respectively. The Fab of anti-CEA antibody variable domain is fused to the Fc-knob domain with a hinge region and the same as the VHH of anti-TNFα to the Fc-hole domain, or vice versa. The Fab-Fc and VHH-Fc fragments can be paired via the interaction of the Fc regions. This BsAb can retarget cytokine (TNFα) to tumor cells. It is designed for the research of Breast cancer; Ovary cancer; Colon cancer; Lung cancer therapy.