Abstract: With the rapid development of Chinese high-speed railway, there are more and more electric equipment and power supply facilities in high-speed trains, and the mechanism of electromagnetic interference (EMI) caused by power supply system of high-speed train and the design of EMI suppression methods are also more complicated. Based on the three most important elements of EMI - the interference sources, sensitive equipment and coupling paths, the main causes of EMI in power supply system of high-speed trains are analyzed, and the relative merits of existing EMI modeling methods and tools are reviewed in this paper as well. In addition, the typical methods of predicting and suppressing EMI of power supply system in high-speed trains are also listed. Finally, the design difficulties and future prospects of EMI are summarized. Systematical references on problems and design of EMI of power supply system in high-speed trains are provided in this paper.