Abstract: The rock mass quality is divided into different grades on the basis of qualitative analysis of rock mass quality and quantitative analysis of related indexes. According to the different quality grades, the slope stability along Xiahekou-Lagushao road section is analyzed by rock mechanical properties. The results show that the joints of intrusive rock group (quartz monzonite, quartz syenite) and metamorphic rock group (migmatite) have minor influence on the slope instability failure. The weathering and poor integrity of metamorphic rock mass (gneiss) reduce the slope stability. The weathering degree, integrity degree, structural characteristics, occurrence and extensibility of structural planes are the major factors affecting the slope stability, with multiple modes of slope failure and degree.