A waterproof and breathable plug includes a plug body having a mounting base, an air vent on the mounting base, a tubular screw rod at one side of the mounting base and arched blocks at the other side of the mounting base, a waterproof and breathable membrane covering the air vent, and a cover member having a cap nut threaded onto the arched blocks and air valves mounted in the cap nut and movable with rotation of the cap nut to adjust the open rate of the opening between each two adjacent arched blocks of the plug body and to further regulating the breathing rate.
