Torsional vibration is one of the manifestations of shafting vibration characteristics，which is in the highest flight in the design of shafting vibration. In practical application, the test and analysis of torsional vibration are usually implemented by hardware，which is inconvenient for the industrial application. A new method of torsional vibration testing based on the high frequency sampling is presented to realize test and analysis of torsional vibration in this paper. In this method, the cubic spline interpolation is used for processing the velocity signal of speed sampled by eddy current sensor or magnetic sensor, while the method of three point convolution correction is used to carry on frequency range analysis. Compared with the results of torsional vibration analyzer, the torsional vibration signal extracted by this method is credible. In addition, the realization of the method provides convenience for the joint test of torsional vibration signal and other vibration signals.