After the building of the power network, many enterprises are faced with a potential information security issue, the unstable factors threaten to the normal operation of the network information system, which is caused by the computer network defects. Aiming at this point, potential security dangers of power network information system were analyzed. Then an index system based on the security evaluation of power network information systems was established. Applying the analytic network process to get the weights of each index, the evaluation process can be accessed by fuzzy comprehensive evaluation method. The weights of each index are decided by ANP, which can remedy the defects of analytic hierarchy process that the interaction among indexes cannot be reflected. Example analysis is... performed by the Super Decisions software to verify feasibility and effectiveness of the proposed evaluation model mentioned in the paper.