Spindle-bearing system plays a crucial role in superhigh speed grinding, which directly affects machining precision, but it is complex and difficult to get the dynamic performance in experiment. This leads to study how to accurately simulate dynamic performance of spindle-bearing system. So a method which springs and damping units imitate bearing support is proposed in this paper. The proposed method can predict the regular pattern which bearing stiffness and damping ratio affect natural frequency and harmonic response. The research demonstrates that the method predicts well the dynamic performance of the spindle-bearing system and it is close to actual condition, therefore, it can be a reference for dynamic optimization design of spindle-bearing system in superhigh speed grinding.