Higher speed of train and the change of environment temperature could have a great impact on normal operation of equipments in the equipment compartment. By using continuity equation, Reynolds-Averaged Navier-Stokes equation, and RNG k-eturbulence model equation, the temperature field in the equipment compartment is simulated numerically when EMU is running at speed of 350km/h on open line. For the heating dissipation of the traction convertor and the transformer in the equipment compartment is higher, this paper creates a 3-D model of interior and exterior flow field of high speed EMU consisting of 5 carriages running at the speed of 350km/h on open line. The temperature distribution of the inner equipment compartments of the model is researched numerically and the detailed information of temperature distribution in each equipment compartment is obtained when the environment temperature is 40℃, 35℃, 30℃, 20℃, 10℃, 0℃, -25℃, -40℃ respectively. The numerical calculation result shows that when the temperature is 40℃, the surface temperature distribution of the traction convertor in the first carriage is about 41.2~45.5℃, the maximum temperature is 52.5℃. The surface temperature distribution of the transformer in the second carriage is about 43~48.1℃, the maximum temperature is 65.4℃. The surface temperature distribution of the traction convertor in the third carriage is about 43.0~46.7℃, the maximum temperature is 68.7℃. Besides, the surface temperature distribution of these three equipments is same in different environment temperatures. The calculation results can give a strong technical support especially for designing the grilles of numbers and location on side skirts, and the layout of the equipments in the equipment compartments of the high-speed EMU.