Abstract: To address the unclear characteristics of interface insulation degradation in high-speed railway power cables under extreme electro-thermal stress in cold regions, we established a short-term overheating test platform for cable systems in a laboratory setting. We simulated the operating conditions of power cables and analyzed the interface pressure variations of cable terminals under low-temperature, short-term overheating conditions. Additionally, we used simulation and mathematical modeling techniques to examine the microstructural changes at the interface and deduced the degradation evolution pattern of insulation matching under these conditions. The results show that, within a single short-term overheating cycle, the synergistic effect of material molecules and gas molecules causes structural changes in the interface cavity, resulting in an initial increase followed by a decrease in interface pressure. As the number of short-term overheating cycles increases, the residual stress gradually accumulates, and interface roughness initially decreases and then increases, leading to different interface pressure variations at various stages. The degradation evolution pattern derived from these results provides a crucial theoretical basis for preventing sudden cable failures.