Abstract: A coupled model of phase field method and finite difference method was established to study equiaxed dendritic growth in the central area of TIG welded molten pool.In this model,some characteristics of welding pool,such as high cooling rate,short solidification time,and large undercooling degree were taken into consideration.Based on the model,simulation of single equiaxed grain growth in the molten pool of pure nickel was performed successfully.Moreover,the change of dendrite morphology and growth behavior with undercooling in welding pool was studied.The simulation results were in good accordance with the stability theory of interface.Meanwhile,the simulation of multiple grain growth was also presented,which reproduced the competitive growing behavior among side-branches.This study lays a good foundation for further research.