Edge cam downward mechanisms supported by rolling element bearings are widely used in many mechanisms. They play a very important role in many aspects. In the studied edge cam downward mechanism, since the impact force applied on the rolling element bearings is too large, some failures will be produced on the component surfaces in the bearings. To overcome these failures in the bearings, this paper developed a stiffness matching method based on the multibody dynamics theory to optimize the impact force applied on the bearings. The results from original case and optimized case were comprehensively compared. The comparison results show that the proposed method can be used to calculate and reduce the impact force and stress of the rolling element bearings in the studied edge cam downward mechanism.