This paper presents an introduction to the approach to the calculation of fractal dimension of grain size distribution and also an analysis of the fractal characteristics of asphalt mixture aggregate.The fractal of dense-graded aggregate is one-dimensional,but the fractal of gap-graded aggregate is two-dimensional.Dc(fractal dimension of coarse aggregate) and Df(dimension of fine aggregate) are used as the indexes to describe the fractal characteristics of asphalt mixture aggregate.Additionally,the fractal gradation theory is put forward,not only used for the design of dense-graded aggregate,but also for gap-graded aggregate.An analysis is made of the relationship between the fractal gradation theory and other gradation theories.The results show that the fractal gradation theory covers the existing gradation methods.The cause lies in the fact that fractal is the essence of aggregate.