The utility model discloses water-saving inlet and drain valves on a water closet, wherein a water replenishing pipe at the upper part of the inlet valve is connected to an overflow pipe on one side of the drain valve, the bottom of the overflow pipe communicates with that of the drain valve, an overflow pipe end cover is buckled on the port of the overflow pipe, the overflow pipe end cover is provided with a water replenishing pipe interface, and the water replenishing pipe at the upper part of the inlet valve is connected to the upper port of the water replenishing pipe interface; the lower surface of the end cover of the overflowing pipe is hinged to a cross rod, the front end head of the cross rod is matched with the lower port of the water replenishing pipe interface, and an overflow pipe float bowl is connected to the rear end of the cross rod in a suspending manner by a suspender; when the overflow pipe float bowl moves upwards, the lower port of the water replenishing pipe interface is open, and when the overflow pipe float bowl moves downwards, the lower port of the water replenishing pipe interface is closed. According to the water-saving inlet and drain valves on the water closet, water replenishment only goes with part of a progress before inflow stops; through setting the position of the suspender on a sliding sleeve, name setting the vertical position of the overflow pipe float bowl in a water tank, the requirements on inflow water level and water quantity needed by siphoning, thus facilitating water resource conservation.