The existing current sampling and PWM duty cycle update methods in AC permanent magnet servo control system have long delay time, which affects the current loop bandwidth and dynamic characteristics of the motor to some extent; to address this problem, the algorithmic delay caused by the control frequency of the current loop is analyzed, based on which the MSMU (Multiple Sample Duty Cycle Multiple Update) strategy is proposed to improve the bandwidth of the current loop. The strategy reduces the average system delay time by performing multiple spatial voltage vector updates at the same time of multiple current oversampling, thus expanding the current loop bandwidth of the control system and improving the system response speed. A retrospective correction control strategy based on switching count optimization is designed to solve the problems of PWM oscillations and excessive controller integration in MSMU, which improves the deployability of the MSMU strategy. Simulation results show that the current loop of the AC permanent magnet servo control system with the new method has higher bandwidth and faster dynamic response speed.