Recombinant Anti-CD28 x Anti-HN Bispecific Antibody (scFv-IgG) is formed by an IgG and two scFv fragments. The scFvs from an anti-CD28 antibody variable domain are respectively connected to the N terminus of the anti-HN 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 retarget T cells to tumor cells. It is designed for the tumor vaccine modification and the research of Tumors therapy.