The invention provides a state evaluation method of a synchronous phase modifier oil system. The method comprises steps of firstly, establishing a state evaluation index system of a synchronous phasemodifier oil system; carrying out qualitative division on the health state of the synchronous phase modulation oil system; carrying out normalization preprocessing on each evaluation index data; judging whether a normalized numerical value of an evaluation index is 1 or not, if so, determining that the evaluation result is a fault, and if not, solving the membership degree of each preprocessed evaluation index, constructing a fuzzy evaluation matrix and solving the weight of each evaluation index, and finally giving a state evaluation result of the oil system in combination with the fuzzy evaluation matrix and the weight. Interference of subjective factors is eliminated, evaluation cost is reduced, the health state of the oil system can be correctly evaluated so that potential faults of the oil system can be found as soon as possible, the service life of the phase modifier can be prolonged, and remarkable economic benefits are brought to users.