In this paper, seven factors are selected. They can influence the occurrence of fall and can be used as evaluation indices. They included phsiognomy, rock property, and structure of rock mass, rock scale, hydrogeological conditions, weathering and land use type. A risk index model is obtained. Four grades are divided according to the dangerous rock stability index: stability, potential unstable, unstable, and very unstable. Results of real examples are consistent with the survey. The results show that much more information is considered in the model and the data can be obtained easily.