Abstract: Modeling and analyzing survivability in network security management systems is a very import research hotspot.There are some imitations in the existing two methods for network security management systems.A method for analyzing the relationship between the nodes is proposed to calculate system survivability，in which the mathematics model is used and the program of the arithmetic is given.This method shows that how an indirect relation of survivability can be established between two indirect nodes.Theoretical analysis and results indicate that the model and algorithm are feasible and effective.The survivability of networks can be evaluated under different states，the applicability and efficiency are better.

Key words: survivability, function of survivability, intermediate-nodes, dataflow

摘要： 对网络安全管理系统建模及进行可生存性分析是一个非常重要的研究课题，但对于大型网络如何建模和评估生存性，尚无较好的解决方案。现存的两种评估生存性的方法存在较大局限性。提出了一种新的方法，分析邻接节点间的关系，用成熟的数学模型进行实现，使网络中间接的两个节点间形成一种生存性关系。理论分析和实验证明：该模型和算法是可行、有效的。可在不同状态下评估网络中可生存性，计算效率、适用性强于以前的算法。

关键词: 可生存性, 可生存性函数, 中间节点, 数据流