[Abstract] Aiming at the uncertainty and ambiguity of the index parameters of power capacitor insulation state evaluation, a state estimation model based on fuzzy matter-element method is proposed. Firstly, through the on-line monitoring technology of the power capacitor insulation state, the characteristic quantities related to the insulation state of the power capacitor are extracted, including the three-phase unbalanced voltage, the actual operating voltage, the capacitance, the dielectric loss factor and the non-electricity monitoring method in the electricity monitoring method. The oil chromatography three ratios establish an indicator system for the evaluation of the insulation state of power capacitors. Then, according to the crystallinity of the isotactic polypropylene film, the insulation state of the power capacitor is divided into three levels of normal, aging, and severe. Secondly, the multiplication integration method is applied to process the analytic hierarchy process and the maximum entropy weight technology method, and the subjective and objective comprehensive weighting coefficients are obtained. Then, the feature quantity is obtained by calculating the blur quantity value from the membership degree, and is characterized by the fuzzy matter element. Finally, the correlation between the unknown insulated state power capacitor and the positive ideal solution is evaluated to determine its insulation state. The example analysis verifies that the state estimation model based on fuzzy matter-element method can effectively evaluate the insulation state of power capacitors.