Abstract: Abstract: The assessment of the importance of network assets of critical information infrastructures is a key national concern at present. To address the problem that the current network asset importance assessment ignores the business chain and thus affects the accuracy and validity of the results， this paper constructs a three-layer coupled network of “information-physical-users” based on the supply-demand relationship of network services， and proposes an asset importance assessment method based on the network percolation theory: we apply the improved network percolation theory to the coupled model and describe the propagation of failure in the network by combining the percolation probability of nodes and the loss of resource delivery capacity of nodes， and then integrate the change rate of maximum service delivery load and user impact level of nodes before and after failure to distinguish the different impacts of nodes. Finally， simulation experiments are conducted in the context of the electric power industry， and the results show that the method in this paper has high accuracy and provides a theoretical basis for the importance assessment of network assets.

Key words: Key words: critical information infrastructure, network percolation theory, critical assets, coupled networks, failure propagation