According to the research of disconnector reliability evaluation is lack of quantitative calculation, so in this paper , we proposed a method that can evaluate reliability of disconnector in quantitatively, The method uses the gray target theory to integrate state sample data of disconnectors and uses analytic hierarchy process (AHP) to determine the amount of state index weights. At last, combining gray target theory with AHP together to achieve the health status of disconnector quantitative classification. we apply this method to the disconnector in Jiangmen Power Supply Bureau of China Southern Power Grid as an example and the result of the calculation is fit to the real situation, which means the method proposed in this paper is effective and has some practical engineering significance. To some extent , it can guide the maintenance of disconnector.