With the development of network applications, the network security assessment has become an important subject of researches on network security. In order to overcome the defects of traditional network security evaluation models, the network security assessment model based on the comprehensive grey relational analysis, which is the organic combination of grey relation analysis and the analytic hierarchy process (AHP), was proposed in this paper. Firstly, the proposed model used the Delphi method to construct the network security assessment index system. Secondly, it utilized AHP to work out the specific weight of each index. Finally, the comprehensive grey relational degree was calculated to evaluate the network security. By means of simulating a campus network with MATLAB, the research results show that the evaluation is more accurate and the proposed assessment method is an efficient, accurate and practical network security assessment method.