The disc steam trap has a valve plate that is both a sensitive component and an actuating actuator. When the device is started, the pipeline is cooled and condensed, and the condensed water pushes the valve plate by the working pressure to discharge quickly. When the condensate is discharged, the steam enters the trap, the volume of the steam expands rapidly, the flow rate of the steam is larger than that of the condensate, and the pressure difference is generated above and below the valve plate, and the valve piece is quickly closed under the suction of the steam flow rate. When the valve piece is closed, the valve piece is subjected to pressure on both sides, and the force receiving area under the valve piece is smaller than the upper force receiving area. Since the pressure inside the steam trap chamber is derived from the steam pressure, the force on the valve plate is greater than the lower surface, the valve piece Close tightly. When the steam inside the steam trap chamber cools down into condensed water, the pressure inside the steam chamber disappears. The condensate pushes the valve piece by the working pressure, and the condensed water continues to discharge, and the circulation works intermittently.