Abstract: The cellular automaton(CA) method has been successfully applied to simulate the microstructure evolution of welding solidification process, which is a powerful tool for simulating microstructure transformation of weld joint and helps to understand microstructure development so as to optimize process parameters and improve the quality of weldment.Solute diffusion during grain growing process in weld solidification is analyzed.A dendritic grain growth model based on CA method is developed to simulate the growths of the equiaxed grain in the center of the melt pool and the columnar grain near to HAZ, the grain morphologies of them are presented as the results of primary simulation, and the simulation results reproduce the growth of the secondary arms and the tertiary arms as well as competitive growing.The results show that the CA method is one of the effective ways to study and simulate the weld microstructure.