Abstract: Based on the three-dimensional shape model of liquid surface of TIG (tungsten inert-gas) weldng molten pool, the process of the arc force acting on the liquid surface was described. The effect of the arc force on the three-dimensional shape of the liquid surface of TIG welding molten pool was investigated by numerical simulation with finite element analysis software Surface Evolver. Under the arc acting on the weld pool, the variation of the three-dimensional shape of the molten pool and the parameters of the liquid surfaces with the arc force value was obtained. The results show that when the shape of the molten pool is constant (the top fusion zone, the back fusion zone and the thickness of the plate are constant), the area of the top liquid surface, the back liquid surface and the solid/liquid interface are all increased with the arc force strength increasing. The extent of the effect of the arc force strength on the top liquid surface is greater than that of the back liquid surface. The results provide a basis for further study on the problems about TIG welding molten pool.