With the extensive application of information and communication technology in power system, power system relies more heavily on the stable operation of communication system. When a communication node is attacked and fails, the propagation of communication node failures across the powercommunication network will eventually lead to a cascading failure of the power information-physical system. Therefore, it is the necessary to to establish practical interdependent networks model, evaluating the importance of the communication network nodes and protecting the key nodes. Firstly, a weighted network model considering the reactance of the power line and the used rate of the information link is established for the unilaterlal networks in the interdependent networks. Then, the importance of two unilateral network nodes is evaluated according to the weighted network node importance evaluation method. Finally, considering the importance of communication nodes, the importance of the inter-network nodes is evaluated based on the internetwork coupling incidence matrix. An IEEE14 bus system is taken as an example to construct a dependent network and evaluate the importance of the communication nodes. The results show that the proposed method r is feasible and can be utilized in practical engineering.