Abstract: According to the configuration design requirements of the air film damper in the aero engines, the mechanics model of the air film damper was built based on the extrusion gap flow theory and energy equation. Therefore, the equivalent stiffness coefficient and the equivalent damper coefficient were obtained. The amplification factor's expression was also obtained through derivation from the vibration equations. Research results revealed that,the air cavity thickness, the initial cavity pressure, the modal frequency and the location of the absorbing vibration plate were the key parameters which determined effect of vibration reduction. The optimization air cavity thickness was determined by the boundary layer thickness and vibration frequency, thus the best value could be acquired according to the particular case in order to depress the vibration response to the maximum extent. The damper coefficient increased with the increase of the initial cavity pressure. The nature frequency of the additional plate was recommended to be close to that of blade, and the absorbing vibration plate was suggested to be installed on the location with the maximum vibration response,in order to obtain the best effect of vibration reduction.