Abstract: The changes of grid-side circuit parameters caused by the external environment and aging of power devices easily affect the control performance of the single-phase PWM rectifier system for the electric locomotive. A μ-synthesis direct current control strategy based on the structure singular value theory is proposed in this paper, which helps to improve the robustness of the single-phase PWM rectifier system under the grid-side circuit parameter perturbation. Based on the dq coordinate mathematical model of the single-phase PWM rectifier, the state space of the current loop system is obtained. The tracking accuracy, anti-interference ability and control output size of the current control system are constrained by the performance weighted function. Meanwhile, the virtual performance uncertainty module is introduced to further conclude the μ-synthesis control problems of the single-phase PWM rectifier with structural uncertainty. The peak value of the structure singular value curve obtained by D-K iteration is 0.895, which shows that the μ-synthesis direct current controller can make the single-phase PWM rectifier system meet the requirements of robust stability and robust performance. The hardware-in-loop system is adopted to verify the proposed algorithm via comparison with the direct-axis quadrature-axis current decoupling control strategy. The experimental results show that the proposed μ-synthesis DCC algorithm has superior dynamic performance and strong robustness when the equivalent inductance parameter perturbation occurs.