The invention discloses an opening and closing mechanism of an overflowing safety valve. The opening and closing mechanism comprises a liquid inlet connector provided with a liquid inlet hole, and further comprises a valve element assembly which can move relative to the liquid inlet connector and is used for controlling the opening and closing of the liquid inlet hole. According to the opening and closing mechanism of the overflowing safety valve, the movable valve element assembly is matched with the liquid inlet connector, and the valve element assembly can be used for controlling the on/off of an oil path from the liquid inlet hole to a liquid outlet hole; when the valve element assembly is far away from the liquid inlet connector, large-flow overflowing can be realized, so that the flow of the safety valve is greatly improved; the axial displacement of the overflowing safety valve can be shortened by short-time rapid overflowing; and the axial displacement of the valve element assembly is reduced so that the axial deformation of a resetting spring is reduced, and finally, pressure fluctuation can be reduced.