Recombinant Anti-CD19 x Anti-CD3 Bispecific Antibody (scFv-IgG) is formed by an IgG and two scFv fragments. The scFvs from an anti-CD19 antibody variable domain are respectively connected to the N terminus of the anti-CD3 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 research of B cell lymphoma; Follicular lymphoma; Leukemia therapy.