In order to escape the pavement destruction caused by the segregation of granular pavement materials, a segregation test was designed according to the segregation process, and a kind of four-element mineral mixture was chosen as the research object to construct a continuous diameter distribution model. Afterwards, the segregability of granular materials was obtained according to the parameters describing the material segregation. The results show that, according to the segregation degree of granular materials evaluated by the difference in diameter dispersion co- efficient, it is convenient to assess the fitness of segregated materials for pavement, and that the segregation degree of granular materials obviously increases with the average diameter and the diameter dispersion coefficient. The proposed evaluation method can also be used to analyze the segregation of asphalt mixture.