Abstract: Driven by SiC inverter, Hairpin winding motor is subjected to complex pulse electrical stress with high frequency and rapid variation. The possibility of insulation failure in motor is greatly increased. In order to find out the voltage distribution in motor windings and to evaluate the insulation reliability, the voltage distribution for a Hairpin winding motor with a rated voltage of 800 V is calculated by the field-circuit coupled finite element method. The voltage distribution rule in the motor winding is obtained by simulation. Through simulation and measurement analysis, it is found that the motor's maximum phase-ground voltage is 540 V, which is located in the inlet end of the three-phase winding. The maximum voltage of turn-turn and phase-phase appears at the positions that are the farthest apart in series sequence in winding circuit but adjacent in space, and the voltages are 575 V and 923 V, respectively. The measurement proves the accuracy of the calculation results. At the maximum voltage point, the error between simulation and measurement is 8%. Based on the simulation model, it is found that 30% of the capacitance variation between turn-turn or turn-ground has no more than 5% influence on the voltage at the key position of insulation. Combined with Dakin formula, the optimization suggestions for the insulation design of motor are put forward. The above results provide reference for insulation reliability evaluation and insulation design for Hairpin winding motor.