Abstract: This research aims to solve the problem of the different degrees of damage in rock mass structural surface and the numerical model selection problem in slope multi-slip surface analysis. With the advantage of the DDA dis- placement calculation,considering the relative displacement between blocks,the slope multi-slip surface search by dy- namic strength reduction-discontinuous deformation analysis method ( hereinafter referred to as DSR-DDA) is pro- posed. Through dynamically reducing different strengths of rock mass structural planes under different degrees of dam- age and dynamically changing the slope multi-slip surface analysis numerical model,the problem of the different degrees of damage in rock mass structural surface and the numerical model selection problem in slope multi-slip surface analysis can be solved. The tilting plane slider classic case is used to test displacement threshold,and also applied to the stability analysis of multi-slip surface of rock high slope in Fushun Western Open-pit Mine,coupled with the self- developed GeoSMA-3D system. The results show that when the displacement threshold is set to 1 mm,the error be- tween DSR-DDA and the theoretical solution is within 0. 5% ,which satisfies the calculation requirements. The most dangerous slip surface (corresponding to a safety factor of 1. 136) of the Fushun West Open Pit Slope is obtained,and it is basically consistent with the potential slip position obtained by analyzing the displacement of the on-site monito- ring. Based on the numerical slope model after the first landslide,the position of the secondary slip surface ( corre- sponding to a safety factor of 1. 189) is obtained. The results are quite different from the con-ventional analysis,which proves the necessity of the dynamic change of the numerical model in the slope stability analysis. The DSR-DDA meth- od has a good coupling effect with the key blocks identified by the GeoSMA-3D system. It proves the practicability of the DSR-DDA method from the perspective of block theory. The failure mode is traction sliding failure,and the middle and lower oil shale plays a key role in slope stability. Therefore,to avoid causing large-scale landslides at the upper part of the slope and landslides at the pit-city boundary,it is not possible to continue the mining of remaining oil shale.