Abstract: The nucleation and growth models of the microstructure formation of spheroidal graphite cast iron from solidification down to room temperature were estab-lished according to the existing solidification kinetics theories. Based on the solidifocation kinetics models, a 3D finite difference code, FTStructure, has been developed to simu-late the formation of microstrucures and to predict the as-cast mechanical properties of the SG iron. The cooling curves, microstructures and Brinell hardness of SG iron speci-mens were simulated. Good agreement was obtained between the calculated results and those of experiments.