High power inverter is one of the most converter devices in wind turbine generator systems, and also has many faults in working. A fault diagnosis method was proposed which combines analytical redundancy with bond graph model for high power inverter. Bond graph model for the system and establishing diagnostic bond graph model were built, with analytical redundancy relationship and its fault characteristic matrix were established at the same time. Fault was detected and isolated quickly through comparing the observed characteristics matrix and fault characteristic matrix. The simulation results in 20-sim demonstrate that the method is convenient and effective for High power inverter fault diagnosis.