In order to comprehensively and objectively evaluate the fire risk of converter transformer, a fire risk assessment method based on the combination of analytic hierarchy process(AHP) and entropy weight method and fuzzy mathematical calculation is proposed. According to the relevant laws and regulations and drawing on the existing research results, fully consider the characteristics of the hazard factors of the converter transformer fire (mainly from seven aspects of insulation performance, insulation oil characteristics, operating conditions, accessories, fuel tanks, environmental factors, fire equipment), Constructed an index system composed of 7 first-level indicators and 27 second-level indicators. The analytic hierarchy process is used to obtain the subjective weight of the index, the entropy weight method is used to obtain the objective weight of the index, and the weights are combined to eliminate the weight error caused by the single weighting method. A ridge-type membership function is used to determine the fuzzy relationship vector of the assessment factors and the fire risk level, and finally the fire risk level is calculated by the linear transformation of the fuzzy relationship matrix and the combined weight vector. Using this method to conduct an empirical evaluation of the five stages of a converter transformer, it is concluded that there are four stages of fire risk rating of I and one stage of fire risk rating of Ⅱ and this stage have weak item u1, u3, u4, u7. Result accords with the actual running situation, and show that the method is suitable for the converter fire risk assessment.