In the traditional design, the surface heat transfer coefficient of brake resistor mainly came from experience or temperature-rise test data, and was not calculated by formulas. In order to calculate the transient temperature-rise of the brake resistor, and validate the design of the brake resistor, a research on the surface heat transfer coefficient of brake resistor element based on numerical method was carried out, and a model for calculating the transient temperature-rise was built based on surface heat transfer coefficient of steady condition. The influence of heat conduction and radiation heat transfer on brake resistor element temperature-rise was also analyzed. By comparing the results with temperature-rise test, the transient temperature-rise model was verified, which provided a simple and effective method for brake resistor temperature calculation.