It is difficult to obtain the globe optimum solution by applying conventional sizing and geometrical optimization methods. Evolutionary topology optimization is conducted for the lower stable of a hydraulic press using a bidirectional evolutionary structure optimization (BESO) method based on ratio of stress changes, and the evolutionary history and index are analyzed. The presented algorithm obtains the simultaneous optimization on both geometry and topology, and a new topology of the lower stable of the press is evolved which possesses a reasonable topological structure. The results of finite element analysis show that the new structure has decreased maximum stress, uniform stress distribution and good material usage.