Water-saving tank cover assembly and water-saving water tank

The utility model discloses a water-saving tank cover assembly and a water-saving tank. Comprising a button module, a tank cover and a drain valve matched with the water-saving tank cover assembly, the button module is fixedly arranged in a frame body on the tank cover and comprises a left self-reset button, a middle self-reset button and a right self-reset button which are arranged in the frame body side by side, the lower ends of the self-reset buttons are connected with extension rods, and the extension rods are connected with the water-saving tank cover assembly. A connecting disc is arranged on one side, far away from the frame body, of the middle key extension rod; a full-drainage key and a half-drainage key are arranged on one side, close to the frame body, of the drainage valve side by side; the left self-resetting key and the right self-resetting key respectively correspond to a full-drainage key and a half-drainage key on the drainage valve; the connecting disc corresponds to the middle of a full-dr