Recombinant Anti-CD3 x Anti-CEA Bispecific Antibody (Fab-Fv) is designed to be expressed as two polypeptide chains. The heavy chain Fd fragment and light chain of an anti-CD3 antibody are fused with the VL and VH domains of an anti-CEA antibody respectively. It can form natural in vivo heterodimerization. This BsAb can retarget T cells to tumor cells. It is designed for the research of Colorectal cancer (CRC); Breast cancer; Lung cancer; Gastric cancer therapy.