Abstract: The information of the structural planes was collected using a contactless photography measurement technique， and then it was imported into GeoSMA3D system which was developed by author to establish the spatial numerical model of rock mass slope. In this way， the key blocks can be defined in terms of dimensions and positions. Then 3DEC was used to simulate the slope excavation and excavation after anchor support. The results showed that the excavation of the rock slope causes the rock internal stress redistribution and a wide range of the shear plastic zone， and the displacement and velocity are heavily concentrated on the joints in the vicinity of the excavation face. The directions of displacement and velocity lean to the free face and their magnitude tends to increase gradually. So if no appropriate supporting measures are applied， the overall instable failure of rockmass slope will happen. After anchor support， the potential slip surface of the slope is controlled and the slope is in a steady state as a whole.

Key words: rock mass slope, key block, GeoSMA3D system, numerical simulation, 3DEC software, anchor support