The invention provides an oil-immersed transformer fault diagnosis method and system and a readable storage medium. The oil-immersed transformer fault diagnosis method comprises the following steps: S1, acquiring corresponding gas contents in different fault states and normal states; s2, screening the gas in the S1, selecting the gas with centrality and integrity as a characteristic gas input model, and performing integer coding on the transformer state corresponding to the characteristic gas as an output result of model training; s3, preprocessing is carried out, and effective data is reserved as a first training set; s4, carrying out layered division, sample synthesis balance and standardization treatment; s5, training and testing are carried out; and S6, carrying out transformer fault diagnosis. According to the invention, the defects of the existing oil-immersed transformer fault diagnosis algorithm based on the traditional artificial intelligence algorithm can be made up, the fault diagnosis accuracy of the oil-immersed transformer is improved, and the power supply reliability is improved.