Abstract. With the improvement of social information network, the information infrastructure confronts with increasing security threats. Governments and security groups are reinforcing research on the complex information systems vulnerabilities and especially the network vulnerabilities. Among them, the defense of network cascading failures is one of the most important safety issues in complex network. This paper made a research on the defense mechanism against cascading collapse effect in communication networks and proposed a defense model based on emergency flow-limiting mechanism. And by using three sample networks in simulation experiments, the plan has been proved working well in controlling and defensing cascading collapse phenomenon appearing in communication networks. At the same time, we conducted some simulating researches and analyses on defense plan of deleting the modules with lower centralization degree. By comparison, we find defense model with emergency flow-limiting mechanism has a wider application scope and higher efficiency, while costing less, providing prominent theoretical support to prevention and control of network cascading failures.