There are a lot of problems in the design, manufacture and operation of high-speed motor. Solving these problems by experience is time-consuming and inefficient. Using the appropriate calculation and analysis software to analyze and optimize the structure can achieve good results. It is an effective method to evaluate the vibration performance of the rotor structure by using the rotor dynamics method, and then optimize the rotor structure. Taking the rotor vibration of a double-shaft-extension motor as an example, the static deflection of the rotor is solved by the beam element method, and the rotor dynamics is analyzed by the finite element analysis software ANSYS to find out the reason of the rotor vibration, and the rotor structure is optimized according to the calculation results and the structural characteristics. The rotor structure of the doubleshaftextension motor is adjusted according to the optimization scheme, and the rotor vibration problem of the motor is solved successfully.