Abstract: Along with the comprehensive effects of both shock waves and expansion waves, the aerodynamic thermal effect induced by the high-speed train in an evacuated tube is severe. As the initial environment can directly affect the aerodynamic performance of the train in the tube, it is of great significance to study the initial ambient temperature effect for the future development of high-speed train transportation in evacuated pipelines. Based on the establishment of a quasi two-dimensional unsteady numerical model with moving boundaries, the aerodynamic characteristics of the train at initial ambient temperatures of 273.15 K, 300 K, 350 K and 400 K are studied. The physical property change of air is worked out using the molecular kinetic theory, the mixed flow state of laminar/turbulent flow is predicted using the SST k-ω transition model, and the transonic motion of the train in the tube is simulated using the moving mesh technique. The results show that with the increase of the initial ambient temperature, the drag of the whole train decreases, and the development of the wake disturbance region slows down, while that of the front disturbance region of the train speeds up. At different initial ambient temperatures, although the wake region is accompanied by vortex shedding, the dominant frequency of the temperature fluctuation is very low, around 0.76 Hz, and the amplitude of the temperature fluctuation is less than 2 K.