对与土木基础设施网络系统防灾优化设计有关的各种单元重要性参数进行了定义及讨论，给出了相应的评估方法；通过单元重要度分析，得出了对基础设施网络系统的可靠度预测、优化设计、维修加固等有工程指导意义的概念性设计准则，大大减少了防灾决策的盲目性及决策工作量。 Various elemental importance parameters related to disaster prevention and optimization design of civil infrastructure network system are defined and discussed. Corresponding evaluation methods are given. Through the analysis of unit importance, the reliability of the infrastructure network system is obtained. The conceptual design criteria with engineering guidance such as prediction, optimization design, maintenance and reinforcement greatly reduce the blindness and decision-making workload of disaster prevention decision-making.