Recombinant Anti-CEA x Anti-DTPA Bispecific Antibody (F(ab')2-scFv2) is designed to be expressed as two chains combined via a hinge region. The scFv of the anti-CEA specificity is fused to the C terminus of the anti-DTPA Fab fragment, or vice versa. This format comprises four binding sites (two same scFv regions and two same Fab fragments), two for each antigen. 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.