The running state of the electric wheel affects the safety of the vehicle directly. It is an immediate emergency to build a condition monitoring system of electric wheel. The primary premise is to select the appropriate signal measuring point position. In order to improve the selected location of measuring points sensitivity for electric wheel state recognition, compounded distinguish index (CDI) is proposed to select the best signal measuring point. Firstly, the method uses modal analysis to obtain the optimal location range of the measuring point, then calculates the CDI of the measured points within the optimal measuring point location range. Finally, it selects the location of the measuring point with the maximum CDI as the optical location.