Abstract: With the torque measurement method using Active Power, torque measurement theory and electrical measurement theory can be combined to measure the active power and the rotation speed of the drive shaft, instead of the measurement of valve torque. In this way, not only the torque can be effectively measured, but also the three-phase motor voltage, current, power, etc.of the driving motor can be monitored at the same time, and thus a more reasonable diagnosis result can be obtained based on comprehensive evaluation. By simulating the various valve fault forms, based on the collection of data and the analysis of signal features, fault database is developed by fuzzy clustering method. By pattern recognition, the real-time faults are analyzed, and the results are given. Tests show that this diagnosis method is simple, effective, and with detailed characterization for a variety of fault modes.