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In order to study the influence of each driving force on the flow of molten pool and its influence degree, separate action models for the arc driving forces were established based on the finite difference method. It is found that the descending order of the driving force influence is surface tension, arc pressure, Lorentz force, drag force and buoyancy when the current is a constant value of 200 A. Based on the calculation of arc driving forces, a transient three-dimensional model of the pulsed TIG welding is established. The alternation of peak current and base current leads to periodic oscillation of molten pool surface and the formation of welding ripples. The results show that the distance between adjacent welding ripples is almost directly proportional to the scanning speed and the molten pool depth decreases with increasing speed and the decreasing speed gradually decreases. By studying the distribution of pressure field and temperature field, it is found that the pressure distribution of a semi-arc column is basically a half-Gaussian distribution and the heat accumulation has a significant effect on the maximum temperature of the substrate.