Recombinant Anti-CEA x Anti-DTPA Bispecific Antibody (CrossMab) is designed to be expressed as four chains with knobs-into-holes mutations and domain crossover. After one or multi-steps purification, high-purity antibody can be obtained. 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.