The smooth pillow is a key component of the Tauren type Electric Discharge Machine (EDM), and the type is a typical cantilever structure. Under the action of gravity and cutting force, as a weak link of a cantilever structure, smooth pillow is easy to deform, which reacts to the spindle, severely degraded the performance of machine tool. The stiffened plate structure of the Tauren type EDMs smooth pillow was analyzed, and a kind of new structure form was put forward. With the specific stiffness as evaluation principle, the optimum structure scheme is gotten, which provides the theoretical basis for the design of Tauren EDM’s moving parts.