This paper investigates the network security problem which is complex to evaluate. The key of this evaluation is to establish the factors and weights. Traditional methodologies cannot get rid of the key issues, resulting incorrect evaluation. In order to improve the accuracy, this paper proposes an evaluation model which is based on analytical hierarchy process (AHP) to evaluate the network security in the real-life background. There are several steps. First, evaluation factors are set up through Delphi method. Second, the weights are determined by AHP. Third, the evaluation is executed. Finally, the real-life cases are used to verify the model. The verification indicates that AHP enables to evaluate the network security efficiently in terms of objectiveness, high accuracy and comprehensiveness.