Abstract：There are many faults and cracks in rock of arch dam abutment. It is appropriate that abutment stability is analyzed by discontinuous media mechanical model. The interface element method(IEM) is well used in the modelling of the displacement discontinuity in the interface of two adjacent elements. It is applicable to describe the phenomena of detachment and sliding between the two elements. The more practicable results may be obtained with the IEM being used to analyze the abutment stability. The concerned variables，such as water pressure，earthquake load，material parameters and so on，are random variables in the study of abutment stability. Structural reliability theory is suitable for the analysis of abutment stability. The abutment rock mass is deformable body，and the stress and deformation of the abutment rock mass are the main indexes in determining the abutment stability. The tensile and shearing strength of faults and interfaces are regarded as the criterion to establish the limit state equation. The response surface method is used in the reliability analysis of abutment. In order to calculate the system reliability of abutment，the stiffness matrix must be modified continuously to analyze the change of the structure. The method is used in an example of reliability analysis of abutment stability，and the obtained result shows that it is suitable for the stability analysis of abutment.
