In order to study the development characteristics of transformer oil fire in the equipment cabin of EMU, the fire model of equipment cabin was established by Pyrosim software, and three typical working conditions were designed to analyze the occurrence and development process of transformer oil fire, and the influence of transformer oil combustion on smoke and temperature in equipment cabin was obtained. The results show that the fire caused by the oil leakage on the right side of the transformer will produce a large amount of high-temperature smoke in the equipment cabin, and the temperature reaches 220 ℃. The smoke generated by the leakage of ester oil at the position of high-voltage bushing and low-voltage terminal sealing ring in the transformer is sucked into the inlet of the cooling fan of the transformer by the velocity flow field in the cabin. There is less smoke in the equipment cabin, and the temperature is lower than 120 ℃. Provide theoretical research for the installation position of fire detector in equipment cabin.