Power electronic transformer（PET）which equipped in electric locomotive can meet the requirements of weight loss，improving power quality for traction system. Single-phase pulse width modulation（PWM） rectifier is an important part of power electronic traction transformer, with the advantages of controllable power factor，fast dynamic response. However，due to the low-frequency fluctuations in the DC voltage，AC current will generate low-order harmonics which will “pollute” the traction network worsen the power quality. Therefore，this paper proposed an improved vector control strategy for the single-phase PWM rectifier of the electric locomotive traction system, the proportional resonant（PR） control is introduced in the current control loop，and based on the analysis of the reason for the harmonic current produced in the network side，harmonic suppression function is introduced into the current loop controller to suppress the harmonic current. Simulation and experimental results verify the effectiveness of the proposed control strategy.