This chapter utilizes digital twin technology and simulation software to analyze the multi-physical field variations of high-voltage onboard equipment, such as insulators and cable terminals, under natural environmental factors. The study reveals that dirt and wet layers significantly alter the surface electric field distribution of insulators, with dry regions potentially causing corona discharge and flashover. Separated water droplets induce local electric field distortions, although the overall potential distribution remains largely unaffected. High-speed airflow exacerbates pollution on windward and leeward surfaces, while optimizing the skirt angle helps reduce dirt accumulation. The stress and temperature of cable terminals are inversely correlated with wind speed—higher wind speeds lower both temperature and stress. In sandy environments, charged sand particles intensify electric field distortions, resulting in a substantial decrease in flashover voltage. These findings, derived through simulation, provide valuable scientific support for optimizing the design and ensuring the safe operation of high-speed train high-voltage equipment.