Assessing the stability of rock slopes is an important and difficult problem. Rock mass classification systems have become a suitable tool for fast assessment of rock slope stability. In contrast to other slope stability classification systems, the slope stability probability classification (SSPC) method has made obvious progress. In this study, numerous excavation slopes were surveyed along the Wentian and Xiaolan highways in the Yunnan province, China and their basic data were collected in the field. From the slopes, we choose some typical excavation slopes with different structure types, such as cataclastic, granular, layered and blocked structures. According to the three-step analysis method in the SSPC system, failure probability of the excavation slopes were assessed based on the possible failure mechanisms and modes of the slopes. The results show that the SSPC method exhibited an accuracy of 70 % in the stability assessment of the highway slopes in the Yunnan province.