The aging feature quantity of transformer oilpaper insulation system is different under different test methods. Some ambiguity and uncertainties still exist in the comprehensive assessment of complex insulation condition. Thus, the transformer oilpaper insulationcondition assessment model is established based on fuzzygray clustering and comprehensive weight method. Firstly, the aging index hierarchical graph based on multiple test methods is obtained.Usingfuzzt C –means clustering (FCM, Fuzzy cmeans), the four levels of the aging state standard index vector table of oilpaper insulation condition assessment is identified and the threshold of whitening function is determined with the collected transformer insulation aging index data. Secondly, the gray clustering coefficient is calculated by assigning weight to the aging quantity by weighting method combined with subjective and objective sense.Thirdly, a comprehensive assessment model of oilpaper insulation state is built taking the gradeone gray clustering coefficient as the membership matrix of gradetwo fuzzy comprehensive assessment. Finally, the validity and accuracy of new assessment method are verified by examples, which shows a good prospect.