Abstract: A three-dimensional model of freely burning TIG arc was developed.By using FLUENT software, choosing appropriate boundary conditions and strongly coupling control equations, TIG welding pool was simulated.Under the action of different parameters, the changing of size and temperature of the pool were analyzed.The results show that with the high current steping to the low current, the pool size and the flow will decrease at some extent.With the step of the welding voltage, welding speed, workpiece thickness and width, the changes show a certain lag.By adjusting the welding parameters, the pool size can be controlled.