During the initial design process of a gearbox, it is difficult to satisfy both of the global mode and local mode characteristics. There is little research on the quick acquisition and modification of unreasonable local structural modes without affecting global modes. A method for the optimization of gearbox vibration based on structural modification of local mode characteristics is proposed. To optimize gearbox vibration, unreasonable local structural responses are obtained using a comparison of local mode frequencies and excitation frequencies. These local structural modes are then modified using topology optimization. The results show that this new method can be used to quickly and effectively control the vibration of a gearbox during the initial design stage and provide an optimum structural design.