Abstract: A water pre-storable toilet includes a drain valve located between an injection duct and a water tank, and a float connected to the drain valve is further provided in the water tank. The float is configured to apply an upward pulling force to the drain valve at least when a water level of the water tank reaches a maximum. The float is also configured in such a way that when the float applies the upward pulling force to the drain valve, a buoyancy of the float may not overcome a water pressure caused by the water in the water tank to the drain valve, a weight of the drain valve itself, and a negative pressure formed when the pre-stored water in the injection duct reaches the highest water level regardless of water level of a water in the water tank and thus can't open the drain valve.