Abstract: In China, there are extensive igneous rocks, which are accompanied by rich mineral deposits. So, it is very important to study opencast mines and open pit slopes in these area.It is considered in this paper that the most significant factor which triggers the movement of the rock mass is fracture structure plane （preferred plane）. Other important geological factors are alteration, tectonic stress and underground water.According to the concept of two preferred planes and based on long term data accumulation we have established six types and fourteen evolutionary models （geo-mechanical models） of the deformation and failure for rock slopes in igneous areas. The practic has shown their universal significance. Through these models we can set up the proper mathematical or mechanical models and evaluate the stability of rock mass both qualitatively and quantitatively.It might be valuable to mention that based oa the analysis methods of two preferred planes, the authors have built five methode for predicting the geomechanical model which may occur in future on these rock slopes.