A drain valve for low-level water tank flushing includes a drain valve body, a low-level washing ring flushing device and a switch assembly. The switch assembly includes a switch element and a switch sheet. The switch element is connected to the switch sheet by using a lifting rod. When the switch element opens a sealing assembly of the drain valve body under the action of an external force, the switch sheet changes a channel between a water inlet and a water outlet from a small opening state to a big opening state.