In the traction electric drive system, due to the characteristics of high voltage and high current, as well as the conditions of switching loss and heat dissipation, the maximum switching frequency of the inverter is usually low, which is only a few hundred Hz. In this case, the current control performance of the permanent magnet synchronous motor control system is poor. For this reason, a discrete mathematical model (impulse transfer function) including the influence of delay was established based on complex vector analysis, and the current regulator was determined by the least-shot system design method. Finally, according to the problem of mathematical model was not accurate at low speed, the compensation plan was put forward. The simulation and field test results showed that the feedback current could follow the given current well and the electromagnetic torque could exactly follow the given torque when using the current controller at big current start and high speed operation conditions. Moreover, the current and voltage have better steady-state and dynamic performance when the gears are added or shifted.