In order to verify whether there is bearing electrical corrosion risk in the permanent magnet synchronous motor(PMSM) equipped with deep groove ball bearings under high voltage operating conditions, this study used bench test methods to deeply analyse the shaft voltage characteristics of a generator and a drive motor suitable for automotive power systems. The results showed that deep groove ball bearings were unable to form stable lubricating oil film capacitances under low speed operating conditions, and there is bearing electrical corrosion risk under the whole operating conditions. In this paper, a motor modification and test method for shaft voltage test was proposed. Based on that, the shaft voltage characteristics of generators and drive motors under different voltages, speeds or torques operating conditions were studied, and the effects of some bearing electrical corrosion prevention measures were evaluated. The experimental methods and conclusions of this study were of significant reference for solving bearing electrical corrosion problems in automotive motors.