The field shaper is one of the important tools for electromagnetic reduction forming of tube. In order to analyze the influence of structural parameters of spiral groove field shaper on the forming performance of copper tube, the reduction deformation of copper tube was simulated by the loose coupling method, and the influences of the ratio of outer diameter to inner diameter D/d, the total height H and the inner shoulder height h of spiral groove field shaper on the forming performance of tube were analyzed. The results show that the ratio of outer diameter to inner diameter is related to the magnitude and action time of the radial electromagnetic force, and the proper outer diameter and inner diameter of spiral groove field shaper can maximize the radial deformation of tube. The total height has a great influence on the eddy current loss of tool. The larger the total heigh is, the larger the eddy current loss is, and the smaller the radial deformation of tube is. The inner shoulder height has a significant influence on the radial deformation of tube and the length of forming area. The greater the inner shoulder height is, the greater the electromagnetic force density acting on tube is, the more concentrated the electromagnetic force is, and the greater the radial deformation of tube is.