The existence of sensor bracket vibration caused by engine vibration rather than its own resonance and its significant impact on torsional vibration measurement are both determined by experimental study. Based on the voltage characteristics of magneto-electric sensor, the expressions of output voltage and instantaneous speed under the influence of sensor bracket vibration are used, and its mechanism is elucidated. At the same time, laws and spectral characteristics of pseudo torsional vibration caused by bracket vibration are studied. It can be shown that its vibration signal amplitude increases with the bracket vibration amplitude. The main components of the signal are the first and second orders of bracket vibration, but the first order is bigger. As the reference voltage approaches zero, the pseudo-torsional vibration signal amplitude decreases. The optimal reference voltage based method for eliminating bracket vibration effects as well as the computation method of the optimal reference voltage are proposed. Simulation and experiment results show that this approach could effectively eliminate the influence caused by bracket vibration for obtaining optimal reference voltage.