A method of controlling an air suspension system may include a first process of determining, by a controller, whether a current situation is a parking situation that requires reduced air pressure in an air spring, a second process of maximizing, by the controller, damping force of a shock absorber when the current situation is the parking situation that requires the reduced air pressure in the air spring, and a third process of reducing air pressure in the air spring, by the controller, by bypassing compressed air stored in the air spring to a reservoir tank.