To promote the safety level of long steep downgrades(LSD), profile design methods for LSD considering of the brake temperature of truck were studied. Seven typical LSD with different length and average grade percentage were selected. Then the influence of operating speed and gross weight on the brake temperature was analyzed. Furthermore, three characteristic values, i.e. the brake temperature of trucks at the end of the LSD, the distance to the beginning of the LSD when brake temperature up to 200 ℃ and 260 ℃ were used to analyze the influence of two different profile design alternatives, one is that unique longitudinal grade is used throughout the whole LSD, another is that different grade percentages are used in different segments, e.g. a steep grade is preceded by a gentle slope. The quantified section classification criterion was presented, and some recommendations were provided. The research shows that from the aspect of reducing the brake temperature of truck, unique grade percentage is recommended. If different grade percentages were used, the difference between any two adjacent segments should be controlled in a small range.