Based on the friction power method, the calculation method of the heat load of the axle mounted disc and the determination of the boundary conditions were studied with axle mounted disk for brake system of CRH2 EMUs. According to the energy conservation method, the heat flux density applied to the surface of the brake disc was simplified and the relationship between the average forced convective heat transfer coefficient and the average natural convective heat transfer coefficient was determined. With ANSYS software, the temperature field distribution and the stress field size of the brake disc of the CRH2 EMUs were simulated. The results showed that: the surface temperature of the train brake disc rised rapidly at the moment of braking, and decreases slowly when the peak value reaches Tmax after t=20 s; After the start of the brake, the thermal stress of the plate increased abruptly, reaching the maximum value of σmax=238 MPa at t=9.6 s, and then gradually declined; The maximum stress value of σmax was much smaller than the maximum allowable stress of the material at room temperature σb=785 MPa, in line with CRH2 EMUs shaft material and structural conditions of use conditions and brake friction requirements and brake system technical requirements. The thermal stress curve and the temperature field distribution curve before and after the peak had a step difference but the same basic trend, which was rising to a maximum rapidly at first and then slowing down.