Abstract: The power monitoring system is not only affected by primary equipment in the power network,but also faces the threat of network attacks at the cyber level. Therefore,it is necessary to evaluate the importance of the communication equipment for the security of the network and the stable operation of large power grids. Considering the characteristics of high coupling between the power monitoring system and power network in general power grids,a two-level power-cyber coupling model is established in this paper. The first level of the model is an interdependent network composed of power plants,substations and dispatch centers at the site. The second level of the model is a complex network composed of communication equipment and power equipment at the equipment level.Secondly,the communication node importance index and the cyber network vulnerability index of the two-level coupling network are constructed. Finally,taking the power monitoring system of a small power grid in Jinan,Shandong province as an example,the paper calculated its network index and has verified the validity of the proposed method. Therefore,the paper is instructive to the risk assessment of the cyber network.