The invention relates to the technical field of fan fault diagnosis, and provides a fan fault diagnosis method based on a three-dimensional membership function fuzzy logic system, which comprises thefollowing steps: firstly, acquiring an actual fan data set, and calculating and predicting the fan data set and a difference fan data set to obtain input data of the fuzzy logic system; Collecting anactual fan training data set, calculating and predicting the fan training data set and the difference fan training data set, and establishing a three-dimensional membership function of the fuzzy logicsystem after selecting the training data set and the reference variable; Then establishing a rule base and a fuzzy device of a fuzzy logic system, fuzzifying input data into an input set, calculatingan ignition level according to the rule front piece set, and calculating an output set according to the rule rear piece set; And finally, obtaining clear output by adopting a gravity center taking method, and judging whether a fault occurs or not according to the relationship between the clear output and a threshold value. According to the method, the membership function and the threshold value conforming to the current environment can be obtained under the environment change condition, so that the fan fault diagnosis accuracy is improved.