Aiming at the problem of the transformer condition assessment of each index in the uncertainty, fuzziness and too many transformer on-line monitoring state information, this paper puts forward a new method of transformer condition assessment based on entropy fuzzy matter-element and principal component analysis. Citing the information entropy which reflects value of the data itself to compute the weight coefficient of index, setting up the model of entropy fuzzy matter-element, and employing principal component analysis method to extract the main components in the information data which effectively solves the difficulty of weight allocation and on-line monitoring state quantity too much. Finally, combined with examples, the validity and practicability of the method is verified.