The invention discloses a burn fault diagnosis method for a slip ring of a generator brush, and the method comprises the steps: simulating a slip ring burn fault through simulation software, carrying out the processing of a fault phase excitation current before and after the fault based on the HHT transformation theory, and finding a fault feature vector; carrying out the actual measurement of the excitation current, carrying out the processing and analysis of the excitation current passing through the slip ring through the Hilbert spectrogram, taking a periodic high-frequency component as the basis for judging whether the slip ring has a burn fault or not, and verifying the feasibility of the method through the comparison with the simulation result. The method based on the Hilbert-Huang transformation theory is accurate and effective, is high in diagnosis precision, and is high in operability.