The invention relates to an independent suspension height adjusting system and method for a multi-axle heavy vehicle. The independent suspension height adjusting system comprises a control valve groupand oil and gas suspensions arranged at both ends of each axle, and the oil and gas suspensions each comprise an upper cross arm, a lower cross arm and an oil and gas spring, the inner ends and the outer ends of the upper cross arms and the lower cross arms are hinged to a frame and a wheel set correspondingly, the upper ends and the lower ends of the oil and gas springs are hinged to the frame and the upper cross arms, a plurality of axles are divided into a front axle group and a rear axle group, the oil and gas springs on the left side of the front axle group communicate with one another through left oil pipes of front axles, the oil and gas springs on the right side of the front axle group communicate with one another through right oil pipes of the front axles, the oil and gas springson the left side of the rear axle group communicate with one another through right oil pipes of the rear axles, the oil and gas springs on the right side of the rear axle group communicate with one another through right oil pipes of the rear axles, and the left oil pipes of the front axles, the right oil pipes of the front axles, the left oil pipes of the rear axles and the right oil pipes of therear axles are connected with the control valve group correspondingly. The independent suspension height adjusting system has the advantages that the structure is simple, the control is flexible andthe adaptability is high. The height adjusting method has the advantages of simple process, reasonable logic and high reliability.