Recombinant Anti-FN1 x Anti-HSG Bispecific Antibody (scFv-IgG) is formed by an IgG and two scFv fragments. The scFvs from an anti-FN1 antibody variable domain are respectively connected to the N terminus of the anti-HSG IgG heavy chains or light chains to form scFv-(H)IgG or scFv-(L)IgG. It is a type of appended IgGs and has 2+2 antigen-binding valency. 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.