Recombinant Anti-CEA x Anti-DTPA Bispecific Antibody (scFv-CH1/CL) is designed to be expressed as two chains. One scFv from an anti-CEA antibody variable domain is fused to CH1 and the other scFv from an anti-DTPA antibody variable domain fused to CL, or vice versa. And the CH1 and CL domains are linked covalently via a natural disulfide bond. 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.