Abstract: An emergency compressed-air brake for automobiles has the advantage to combine integrally the emergency braking, the service braking and the parking braking, which can be widely used in various road vehicles. The combined braking air-chamber involved is simple in construction. The thrust of braking includes two parts, the air pressure thrust and the spring thrust, with the resultant force of the two thrusts as a service braking thrust, with the spring thrust as a parking and emergency braking thrust. Since the spring force throughout joins in the braking, the braking gets more smoothness and is able to anti-locking.