Abstract: In order to evaluate the stability of slope rock mass after excavation and to guide construction safety，based on the discontinuity measurement and engineering survey，the characteristics of discontinuity distribution and rock mass′ structure in Songshunangou Mining Area were analyzed，thus obtaining the advantage discontinuity which controls the slope stability.Three-dimensional network simulation technology was used to make simulation on the advantage discontinuity above and establish the network model to represent the rock-mass′s structure.The network model was cut along each measuring line in parallel or perpendicular direction.It is found that rock-mass were cut seriously by the discontinuity，which provides favorable conditions for the formation of small-scale movable ore blocks.The fractal dimension of each section was calculated by the fractal geometry theory，finding that rock mass is in general or poor state.With the aid of the finite difference software FLAC3D，the stability of rock mass after excavation was calculated.The results showed that due to the excavation and unloading，larger displacement and plastic zone in some parts of slope were generated，possibly resulting in collapse and slippage.It fits with the quality assessment，so reasonably lowering the step slope angle is recommended.

Key words: Rock mass structure, Fractal theory, Network simulation, Quality evaluation of rock mass