In order to achieve recognize the IGBT faults of SVG inverter, a method for fault diagnosis is proposed based on FFT analysis and the neural network. Firstly, using FFT analysis to ananlysis the H inverter output voltage signal , finding the harmonic content of the rule, the higher the harmonic content of the signal is put as a characteristic harmonics. Finally, the neural network is used to achieve the positioning of faulty components. The experiment shows that the fault diagnosis method can effectively achieve to locate faulty components.