Abstract: An information security assessment framework is established for the WAMS communication system. Based on the function tree model and the ISO/IEC 27002 standard, the WAMS system is divided into several sub domains, and the information assets are identified. Combining the function with the assets, the hierarchical structure of the evolution is established for the information security of the WAMS system, and the key values for the sub functions and assets are distributed. The evidence theory is used to integrate the decision data of experts, which reduces the fuzzy of information generated from the assessments of different experts. Example analysis shows that the established framework and the assessment method are useful to improve the information security of the WAMS system. The framework can also be effectively used in other aspects of the security assessment of power systems.