The magnetic flux density in the clearance and the structural parameters were designed for the U-shaped electromagnet of Low-speed EMS Maglev Trains. The magnetic flux density in the clearance was chosen as the magnetic flux density when the permeability of the iron core material decreased to ninety percent of its maximum value. The related structural parameters are the length and the width of the magnetic pole, the width and the height of the window, and the depth of the yoke. It was represented that the length of the magnetic pole has effects on the turning capability of the maglev train, the width of the magnetic pole has effects on the carrying capacity and the guiding stiffness of the train, the width and height of the window has influence on the weight of the train, which should be determined by the width of the guide way, and the depth of the yoke should be chosen according to the principle that the magnetic flux density in the magnetic yoke equals to that in the magnetic pole.