Abstract: A torsional vibration identification method for shafting of pumped storage unit based on hydraulic pulsation was proposed. The dynamic random torque signal was obtained by using strain measurement technology. Setting the trigger threshold, a group of sample signals was obtained by using the intersection point of the signal, the threshold and the points of a certain length. After averaging a sufficient number of sampled signals, the random response and positive/negative velocity impact response were averaged out, and the remaining signal was the amplitude impact response signal. The torsional natural frequency and damping could be obtained by fitting the impact response signal with exponential function. The method was applied to identify the torsional characteristics of a pumped storage unit. The test results show that the hydraulic fluctuation is larger under 25% load condition. The trigger threshold has little influence on the identification results. When the load increases, the torque pulsation decreases. The trigger threshold has little effect on the identified frequency, but it will affect the identified damping. This method does not need to apply torque excitation. It realizes the identification of torsional vibration characteristics under installation conditions, which has a good engineering application value.