In the tube electromagnetic bulging, the length and outer diameter of driving coil are the main geometric parameters that affect the distribution of electromagnetic force and the axial tube uniformity. Based on this, this paper explores the influence of these two parameters on the relative uniform deformation of workpiece in electromagnetic forming from the aspects of magnetic force line characteristics, radial electromagnetic force distribution, axial relative length and so on. The results show that the changes of the height and outer diameter of the forming coil modify the characteristics of the magnetic force line and the electromagnetic force distribution at the end of the tube, hence compared with the short and coarse driving coil, the proportion of uniform deformation on the bulging axis of the tube with slender coil is increased by nearly 42%. Obviously, the tube electromagnetic bulging based on slender driving coil is easier to achieve axial uniform deformation, this study provides.