In order to analyze the electric field distribution characteristics of pump accumulator rotor winding under low frequency PWM voltage and explore the difference of electric field of pump accumulator rotor end under low frequency voltage and power frequency voltage, a three-dimensional finite element simulation model of rotor winding was established based on comsol software. The electric field and potential distribution of rotor windings at low frequency 5Hz and power frequency 50Hz are analyzed. Further analysis was performed by changing the voltage polarity and other parameters. The results show that under the rated voltage of 3kV, the electric field distortion position of the rotor winding is at the end Angle, and the maximum electric field intensity is about 10 5 V/m. Compared with the lower end Angle potential under power frequency voltage, the winding end potential at the same rising edge under low frequency voltage is higher. The low frequency voltage makes the rotor winding end of pumped storage motor more prone to corona discharge.