This paper proposed an effective intelligent model to calculate a health index for distribution transformer using the nonlinear fuzzy analytic hierarchy process (NFAHP). The proposed method depends on the preventive test analysis of distribution transformer, and the key characteristics quantities of distribution transformer are chosen by the expert experiments and actual situation. The weights of characteristic quantities are obtained through the nonlinear fuzzy analytic hierarchy process (NFAHP). Then, the health index (HI) of distribution transformer is obtained through the fuzzy comprehensive evaluation. An intelligent maintenance model is built with filed example to demonstrate the effectiveness of the proposed model in assessing the health condition of distribution transformer. Example analysis shows that the method is correct, clear and close to the true health condition of the distribution transformer.