Abstract: ［Objective］ The grid-side converter is a core electrical component in high-speed railway EMU traction drive system, and its reliability is directly related to the safe operation of the train. Therefore, it is essential to simulate and analyze the temperature rise characteristics of the grid-side converter in high-speed EMU to explore the relationship between temperature rise, operating conditions, and environmental factors, providing theoretical support for temperature evaluation during actual train operation. ［Method］ The temperature rise characteristics of power devices are examined, and an electrothermal simulation model is established incorporating the power loss model and thermal network model. The former is used to quantify the losses of power devices under different operating conditions, while the latter simulates internal heat conduction and dissipation processes of power devices considering the train′s operating environment. The simulation accounts for multiple influencing factors such as operating conditions and ambient temperature, dynamically analyzing the temperature variation trends of power devices and their impact on converter performance. ［Result & Conclusion］ Simulation results demonstrate that the established electrothermal simulation model accurately reflects the temperature rise characteristics of power devices. This research provides critical data support for evaluating temperature changes in grid-side converters during actual train operation.