The invention discloses a switching mechanism for a large-flow overflow safety valve. The switching mechanism comprises a liquid inlet joint with a liquid inlet hole and further comprises a valve element assembly which can move relative to the liquid inlet joint and is used for controlling opening and closing of the liquid inlet hole, the valve element assembly comprises a nut and a valve pad arranged in the nut, and the valve pad is provided with a seal surface used for being matched with the liquid inlet joint, wherein a conical surface is adopted as the seal surface. According to the switching mechanism for the valve element assembly, by arranging the movable valve element assembly to be matched with the liquid inlet joint, the valve element assembly can be used for controlling connection and disconnection of an oil way from the liquid inlet hole to a liquid outlet hole, large-flow overflowing can be achieved when the valve element assembly is far away from the liquid inlet joint, the safety valve flow is greatly increased, axial displacement of the valve element assembly can be reduced through short-time quick overflowing, axial deformation of a reset spring can be reduced through axial displacement reduction of the valve element assembly, and pressure fluctuation can be reduced finally.