This chapter focuses on the digital twin modeling of high-speed train traction power supply systems, integrating mathematical, physical, and multi-physics models to simulate and analyze complex operational conditions. Key system components, including vehicle cable terminals, lightning arresters, and high-voltage transformers, are modeled using finite element methods to address the limitations of traditional testing, such as high costs and inefficiency. The framework combines Maxwell’s, Fourier’s, and Navier-Stokes equations to model electromagnetic, thermal, and flow fields, capturing their interactions through multi-physics coupling. Environmental factors like pollution, rain, airflow, and temperature fluctuations are considered, revealing their impact on electromagnetic, thermal, and stress distributions. For instance, polluted surfaces alter conductivity, affecting heat flux, while high-speed airflow influences heat dissipation and structural stress. High-quality meshing techniques ensure reliable numerical simulations, balancing computational efficiency and accuracy. The chapter highlights the application of digital twins for real-time condition monitoring, fault diagnosis, and optimization, providing a robust tool for enhancing the performance and maintenance of high-speed train traction power systems.