Recombinant Anti-FN1 x Anti-HSG Bispecific Antibody (Minibody) is designed to be expressed as the anti-FN1 scFv fused to N-terminus of Knob-CH3 domain and the anti-HSG scFv to the Hole-CH3 domain, or vice versa. The CH3 domains are further stabilized by C-terminal disulfide bonds. 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 Solid tumors imaging and therapy.