Abstract: Effect of vanadium on continuous quenching bainite ductile cast iron and its existing condition have been studied. Effect mechanism of Vanadium on structure and mechanical property of bnainite has been discussed. It has found that vanadium exists in the forms of both solid solution and dispersion carbide in continuous quenching bainite ductile cast iron. Addition of vanadium to ductile cast iron can increase the nucleation rate of bainite efficiently, facilitate the bainite transformation, refine and strengthen the matrix structure, and raise its hardness. It showed that the vanadium can be used to replace Mo,Ni and B to produce BDI.