Abstract: It is known that the stability of the bedding slope of expressways directly affects the running safety of road, so it is important to summarize its characteristics and determine its study methods. Thus this paper presents a summary of its characteristics and an optimum design method and clue for field investigation, stability evaluation, determination of the optimum excavation slope angle and slope improving design. Then, taking the southern part of Dawu Section of Jingzhu (Beijing-Zhuhai) expressway as an example, we discuss the application of this optimum design method. Namely, the slope stability is evaluated with the method of residual pushing force and the Sarma method based on the analysis of the engineering geology conditions. After that, the sensitivity analysis for the slope stability is done using the residual pushing force method. On the precondition of ensuring the whole stability of slope and the economic reasonability, the paper also advances the optimum angle of design, the slope excavation scheme and the anchor and spray concrete scheme of the slope improvement design. The example shows that this optimum design method and clue are systematic and practicable for the construction.