The utility model relates to a shaft coupling specifically is the prevent shaft coupling that turns back that can transmit one -way moment of torsion. This prevent shaft coupling that turns back has two half -coupling, and one of them half -coupling is activity half -coupling, and another half -coupling is activity half -coupling, perhaps for fixed half -coupling, half -coupling's tip forms two perpendicular mating surfaces that the orientation is opposite, when two half -coupling's tip was relative, its two perpendicular mating surfaces were two double -phase to the cooperation to can be when two half -coupling be rotatory in opposite directions spacing and transmission moment of torsion each other, simultaneously can two half -coupling when the back of the body is rotatory mutually unable circumference spacing, but the axial is pushed open each other, activity half -coupling's back end is provided with compression spring, compression spring's spring force makes two half -coupling tip have the trend of being close to mutually. The utility model discloses can reliably prevent reversal, simple structure, manufacturing and simple to operate, with low costs.