The invention discloses a transformer fault diagnosis method based on an entropy weight method and grey correlation analysis, belonging to the technical field of transformer fault diagnosis. The transformer fault diagnosis method comprises the steps of: carrying out standardization processing on transformer fault sample data; adopting the entropy weight method to determine weight of a transformer fault diagnosis index; and determining a fault type of a transformer through calculating Grey Euclid weighted correlation degree. The transformer fault diagnosis method makes full use of all information of gas in oil data, exerts the advantage that the grey correlation is applicable to a small sample and poor information system, avoids defects of partial correlation and information loss, and can effectively increase accuracy rate of transformer fault diagnosis as shown by results of example analysis.