Abstract: Air springs with cord-rubber structure have the advantages of variable stiffness, lightweighting and better isolating effect, which have become the highlights of vehicle research in the current of new developing trends of automobile. However, as an important parameter, the effective area of air spring is lack of thorough predictive theory. A predictive analytical method for effective area of rolling lobe air spring for vehicles was put forward based on composite material mechanics and the geometrical characteristics of air spring bellow. A predictive formula of air spring effective area was given manifesting the influence of various parameters especially pressure inside bellow and air spring height on effective area. Experiments were conducted using mechanical test rig with certain air spring and the results of test fit the theory well. The errors of theoretical prediction can be less than 1% compared with experiment data. The method is useful for effective area prediction and accurate modeling as well as the height control of air suspension.