The impact of failures in the information network on a power system is seldom， if ever， considered in the conventional research on cascading failures in power systems. Therefore， the information network is integrated with the hidden failure model to investigate the impact of node failures in the information network on the cascading failures in power systems. Take the New England 39-bus system as an example. A new index is used to identify the key-buses causing large blackouts. The index is very effective in identifying the key-buses which exert vital influence on blackouts in power systems operating in various states. Simulation results show that the failures of the information network may make the situation even worse and lead to large blackouts. Moreover， high-degree and， in fact， high-betweenness nodes in the information network， are not the key information nodes that generate important influence in the spread of cascading failures. Rather， compared with the topological characteristics of information nodes in their own network， the physical characteristics of the information nodes corresponding transmission lines are better able to characterize the importance of information nodes in the cascading failures of the power system.