Recombinant Anti-CEA x Anti-DTPA 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-CEA antibody variable domain is fused to the Fc-knob domain with a hinge region and the same as the scFv of anti-DTPA 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 be used in pretargeting system of PET, radioimaging or radiotherapy. It can mediate targeting of radioactivity to tumor cells. It is designed for the research of Breast cancer; Ovary cancer; Colon cancer; Lung cancer imaging and therapy.