Slope safety stability is the bottleneck problem for the development of mountainous highway, especially high class highway in China, which results from greatness slopes along highway in mountainous area, complex geological environment and short forming age. The important degree arrangement of various indexes was carried out based on simple dependent function. And weighting system of indexes was modified with analytic hierarchy process and expert reliability. With indexes and weighting system, matter element extension model for highcutting slope along highway in mountainous area was proposed by matterelement extension method. A case study was undertaken for K88+680 highcutting slopes along WushanWuxi road in Chongqing city based on the model. It was indicated that the safety grade is Ⅲ and the slope is instable.