Abstract: Based on the new idea of controlling welding stress with trailing electromagnetic force, the electromagnetic force in flat spiral coil-aluminum sheet system was simulated with finite element software ANSYS.Effect of geometrical parameters of coil on electromagnetic force was analyzed.The results show that the electromagnetic force acts on the location where the coil projects on the sheet. With decreasing outer diameter of the coil, the electromagnetic force peak magnitude increases and the peak position of the axial force moves linearly close to the inner side of coil.With increasing inner diameter, the radial force peak magnitude increases, the axial force peak magnitude increases first and then decreases, and the peak position of the axial force is fixed first and then moves close to outer side of coil.With increasing wire width, the electromagnetic force magnitude increases.The variation of the position, where the direction of the radial force is turned, with the inner and outer radius is similar to that of the peak position of the axial force.While controlling welding stress based on electromagnetic force, the coil with the smaller outer radius and the appropriate inner radius should be selected, and the magnetic medium is needed to enhance electromagnetic force.