In this study, the continuum-discrete coupling method is be used to an open-pit iron mine slope in Hebei province. The deformation and stress characteristics in the typical across-section of the slope excavated in the difference time steps are simulated in combination with the strength reduction method. Continuum and discrete region are analyzed with FLAC and PFC procedures respectively. Emphatically in terms of the data consistency for continuum-discrete models, the relations of shear strain increment formation, development with local displacement, the force and displacement transformation process of continuum and discrete media, meso-crack of discrete media and plastic deformation of slope mass and so on, the applicability of the continuum-discrete coupling method are studied. Based this method, the instability mechanism of the slope is illustrated from macro and micro aspects. The results show that, stress and displacement of slope in the continuum and discrete region maintain a superior consistency in the process of computation, showing the continuum-discrete coupling method is applicable to slope stability analysis; the varition of shear strain increment acting as slope instability criterion is controlled by horizontal displacement of rock or/and soil mass; the meso-crack mechanism can characterize macro plastic deformation effectively; the change of contact force chain direction between soil particles is the driving factor of displacement and deformation of soil mass.