In order to predict the acoustic absorption characteristics of porous asphalt mixture based on design parameters in design stage, a new acoustic absorption model of porous asphalt mixture was proposed based on its micro structure. The acoustic impedance and coefficient of acoustic absorption of porous asphalt mixture were calculated with the electro acoustic analogy theory. The diameter of characteristic air void of porous asphalt mixture was proposed by using image analysis techniques and statistical analysis theory. The capillary structure values of micro element were obtained by analyzing the relationship between length of capillary and sphere capillary diameter ratio of micro element. Results show that there is a good correlation between the predicted maximum coefficient of acoustic absorption and responding frequency, using this acoustic absorption model of porous asphalt mixture, and tested values with standing wave tube. Ultimately, this acoustic absorption model of porous asphalt mixture was verified as a powerful and robust tool in modeling and predicting the acoustic absorption characteristics of porous asphalt mixture.