Abstract: The percentage of flow discharge is an important concept and tool proposed by the author to study non-equilibrium transportation of nonuniform sediment.In this paper the definition and expression for the percentog of flow discharge are presented.And then the three characteristics are revealed: the carrying capacity of the nonuniform sediment being able to expressed as the summation of uniform sediment using the percentage, the percentage of flow discharge equaling to size distribution of the bed material, and the percentage being the same as the percentage of energy.Based on the concept of this percentage it is proved that the bed material load, the wash load and the total load follow the same rule of the carrying capacity, and the composition of the carrying capacity and the expressions of size distribut ion of the carrying capacity and the effective bed material all can be derived.