The utility model discloses a pulse-type gas supplying device under constant pressure comprising a main body, an air inlet and an air outlet mounted thereon. Inside the main body of the device is disposed a start and stop device to inject to the air inlet constant pressure at intervals. The air inlet passing the gas supplying device is connected with a motor-driven air pump; the air outlet, however, is connected with the tire or other devices. Arranged in this way, a pulse-type gas supplying effect under constant pressure can be achieved.