A big sample of beam specimens of asphalt mixtures was used to carry out strain-control fatigue tests under the same conditions. I MAQ digital image processing was used to process and analyze the inner structure and composition of the flexural section at the centre of the beam specimens through fatigue tests. In this way, the indices of the inner structure and composition of asphalt mixtures wreindentified. Furthermore, SPSS was used to establish a model on relationship between results of fatigue tests and indices of its inner structure and composition. The analysis result shows that fatigue properties of asphalt mixtures are directly correlated with the indices of its inner structure and composition, and the difference in the inner structure and composition of asphalt mixtures causes the significant difference in fatigue properties under the same conditions, which unveils the laws of effect of the inner structure and composition of asphalt mixtures on fatigue properties.

       Key words: asphalt mixture; inner structure and composition; digital image processing; fatigue properties