In order to quantify the building loss during the subway fire, this paper proposes a loss assessment method. This method uses the disaster temperature and the disaster area as indicators to establish a two-dimensional risk loss matrix, and at the same time obtains the building loss evaluation level based on Pyrosim software simulation. Finally, an example of subway train fire is introduced, and the central and end fires of the subway train with a scale of 7.5MW are set up to verify the evaluation method. The result shows that the building loss caused by the subway train fire in the two scenarios are both level III, but the highest temperature of the high-temperature smoke generated by the end fires of the subway train under the same scale at the platform ceiling is significantly higher than that of the central train fire.