Mathematical and computing model of simulating microstructure during solidification process of metal was introduced. Several physical models for the nucleation and growth of grains were presented. The principle of Cellular Automaton(CA) algorithm and its development were introduced. The application of simulating the microstructure transformation process using cellular automaton was described in detail. CA method takes into account nucleation and growth kinetics. The variation of fraction of solid and release of the latent heat can be calculated by coupling calculation of macro/micro modeling. Two coupling calculation modes of the CA and FE methods were presented . The development prospects of cellular automation were forecasted finally.