Aiming at the complexity of high arc dam, and the limitation of conventional methods static and rigid body hypotheses of conventional slope stability analysis, which bring great difference with true engineering state. The paper proposed a concept of “abutment safety degree” considering the affection of dam body, and developed the model including dynamic contact element reflecting local rock crack and quasi continuous medium reflecting large deform. Based on above model, combing with 3D element strength reduction method and strain control criterion, the resist safety degree calculation method for dam shoulder high slope of high arc dam system has been constructed, which can fit the complex geo-mechanical engineering. Finally, the method is used in the dam shoulder slope analysis of Xiaowan arc dam system with height of 300m, the result is satisfied, the calculated safety degree is decreasing 20% to the result of conventional method. The method provides a powerful way to the safety evaluation of complex engineering.