[en] The hysteresis tuning is of great significance before the two-dimensional (2D) molybdenum disulfide (MoS_2) field-effect transistors (FETs) can be practically used in the next-generation nanoelectronic devices. In this paper, a simple and effective annealing method was developed to tune the hysteresis voltage in 2D MoS_2 transistors. It was found that high temperature (175 °C) annealing in air could increase the hysteresis voltage from 8.0 V (original device) to 28.4 V, while a next vacuum annealing would reduce the hysteresis voltage to be only 2.0 V. An energyband diagram model based on electron trapping/detrapping due to oxygen adsorption is proposed to understand the hysteresis mechanism in multilayer MoS_2 FET. This simple method for tuning the hysteresis voltage of MoS_2 FET can make a significant step toward 2D nanoelectronic device applications.