安全保障系统是指功能一旦失效将引起生命、财产的重大损失以及使环境遭到严重破坏的系统,通过对其性能的全面分析和指标的精确计算可以有效降低风险,提升系统安全性.本文利用系统Signature建立数学模型,对该系统的危险失效Signature和安全失效Signature进行定义和算法求解,探索两种失效模式下的系统性能.同时定义了危险、安全失效概率指数,精确计算系统失效时每种失效发生的可能性.最后以数值算例形式给出其算法求解和过程.“,”The safety ensuring system is a system whose failure will cause an enormous life and property loss,and seriously damage environment.Analyzing its function and calculating accurately its indexes can effectively reduce risks and improve the system safety.By using system signature to build mathematics models,this paper defines and solves fail-dangerous (FD)signature and fail-safe (FS)signature,aiming at exploring its function in two modes.Besides,it defines FD and FS probability coefficients,and calculates them when system fails.Finally,this paper gives some examples to show the process of these algorithms.