Abstract: Combining with research on the stability of rock mass in two state key projects,i.e. underground building of Xiaolangdi and foundation o f Jiangyin Bridge,the main problems of stability analysis of layer jointed rock mass such as geol ogical model, calculating parameter and method are discussed. The establishment of geological model and integrating method for determination of calculating para meter is proposed. By using the method of non-liner FEM with consideration of the deformation of geological structural plane, the results agree approximately wi th the monitored results during construction.