The invention discloses a dual waterproof breathable cap, which comprises: a sealing piece, which is a hollow cylinder; a ventilation device, which is connected to the sealing piece and comprises a double-layer waterproof ventilation film and a connecting ring arranged in the middle of the waterproof ventilation film, with the connecting ring being connected to the waterproof ventilation film through hot melting; a cover body, which is arranged at the top end of the ventilation device, is equipped with a through hole, and is provided with first mounting check blocks around the cover body; a cap body, which covers the ventilation device, is internally equipped with a second mounting check block spaced from the top of the cap body, wherein the spacing is equal to the height of the first mounting check blocks, and the first mounting check blocks abut against the second mounting check block. By arranging the ventilation device, invasion of external water vapor, dust, greasy dirt and otherdirt is avoided, fog formation of headlamps in the driving process of an automobile is avoided, the headlamps the automobile can be guaranteed to not to form fog in the driving process, and safety isimproved; and the first mounting check blocks and the second mounting check block are arranged, so that the ventilation cap is precise in position positioning and ingenious in connection.