Based on digital image processing technique, the fractal characteristics of asphalt mixtures with volume composition as research object was studied. The fractal characteristics of aggregate particles, air voids, and voids in mineral aggregates was analyzed, then the calculation method of fractal dimension was put forward. Test results indicate that the slit island method can be used to describe the fractal characteristics of aggregate particles and air voids, the box counting method can be used to describe the fractal characteristics of voids change in mineral aggregates of asphalt mixtures under the effect of loading.