An air release valve and an air pressure driven toilet water tank drain valve are provided. The air release valve includes a valve seat, a sliding block, and a push block. A bottom of the valve seat is provided with an air release channel, one end of the air release channel is an air inlet, and the other end of the air release channel forms an air release nozzle. The sliding block is located above the air release nozzle and is slidably arranged on the valve seat. The air pressure driven toilet water tank drain valve includes a drain valve body, an inner core tube, a limit device, a telescopic airbag, an air pump, the air release valve, a controller and an electronic induction switch. The air release valve with mechanical structure does not require power consumption and has low cost.