Based on the complex and networking characteristics of the combat system under the informationtization condition, combining the complex network theory, the author put forwards three network extension rules and established the network-based system model. Meanwhile, this article discussed the network characteristic parameters, reliability assessment and some other problems, and further relied on the simulation to analyze the network characteristics, reliability and the vital nodes mining under the different extension rules. The research methods and conclusions in this article can be used as the combat system’s arguments and references to its optimization.