Abstract: The railway traction power supply system generally uses single-phase power frequency AC to supply power to locomotives, which inevitably leads to power quality issues such as harmonics and negative sequence currents. As the train continues to develop in the direction of high-speed and heavy-duty, the problems such as high-order harmonic resonance caused by the traction network are becoming more and more serious. Therefore, this paper utilizes specialized power quality measurement equipment to conduct power quality monitoring of a typical traction substation. Based on relevant national standards, a quantitative analysis of the harmonic issue is conducted. Additionally, simulation models including the traction network, locomotive load, and other relevant components were established, and harmonic mitigation strategies were investigated, providing valuable reference for the comprehensive management of railway harmonic issues.