Recombinant Anti-CD55 x Anti-CA9 Bispecific Antibody (scFv-CH3) contains two chains. The anti-CD55 scFv is fused to the Knob-CH3 domain via a hinge region and the same as the anti-CA9 scFv to the Hole-CH3 domain, or vice versa. The KIH CH3 domains can facilitate to form a heterodimer and this bivalent binding leads to improvement in avidity. This BsAb can recruit complements to tumor cells. It is designed for the research of Renal cell cancer (RCC); Solid tumors therapy.