The present invention discloses an improved sliding-mode control method of a V/v tractive power supply system. The method comprises the steps of: controlling load voltages of two supply arms by a railway power regulator connected between the two supply arms through adoption of an improved sliding-mode control strategy; employing wavelet transform and a single-phase phase-locked loop to obtain phases of load currents of the two supply arms according to the instantaneous values of the load currents of the two supply arms, and obtaining the effective values of the load currents of the two supplyarms based on the instantaneous reaction power theory; obtaining the effective values of the reference instruction active currents and the effective values of the reference instruction reactive currents of the two supply arms according to the phases and the effective values of the load currents of the two supply arms to obtain the reference instruction currents of two converters; and obtaining theoutput voltages of the converters by employing the improved sliding-mode control strategy to allow the output current of the railway power regulator to be tracked and controlled. The method providedby the invention achieves accurate tracking for the compensation current of the railway power regulator, reduces the influences of harmonic waves and a negative-sequence current and obviously improvethe electric energy quality of the V/v tractive power supply system.