Many researchers explore the issue about how to predict equipment failures and how to analyze the cause of the failures and to solve them. The mass imbalance is the most common cause of the malfunction of the rotating machinery. Based on the theory of rotor dynamics, we can diagnose the failure and its causes more accurately by applying the software to doing simulation analysis of characteristics of rotor dynamic. And, it provides the reliable basis for the further solutions of the failures. In this paper, we analyze a corporation's compressor with abnormal vibration in operation, and finding out the reasons for its vibration. According to the calculated results, we transformed the local structures of its rotor. After transformation, the compressor runs smoothly.