The invention discloses a compound fault diagnosis method for clamping diodes and supporting capacitors of an inverter. The method comprises the following steps: establishing a three-level inverter compound fault model through simulation software; respectively acquiring three-phase current signals on an output side of the inverter under the normal working conditions and under the condition of each compound fault, carrying out decomposition of three-phase currents under each condition through EMD, and constructing fault feature vectors by using correlation coefficients as fault features; carrying out normalization processing of the fault feature vectors, inputting each normalized feature vector as a training sample into an SVM classifier for training, and optimizing SVM parameters through the genetic algorithm, so as to obtain trained SVM classifiers; and acquiring inverter fault signals to be diagnosed during a testing phase, constructing the fault feature vectors through the same method, inputting the fault feature vectors into the trained SVM classifiers for testing, and outputting fault diagnosis results.