Recombinant Anti-CD22 x Anti-saporin Bispecific Antibody (Fab-Fv) is designed to be expressed as two polypeptide chains. The heavy chain Fd fragment and light chain of an anti-CD22 antibody are fused with the VL and VH domains of an anti-saporin antibody respectively. It can form natural in vivo heterodimerization. This BsAb can be used in pretargeting system and deliver immunotoxin to tumor cells. It is designed for the research of Lymphoma therapy.