Abstract：Material transportation in water fluid mainly depends on two main movements, which are rolling transportation and suspending transportation. The transportation and deposit regulation are different in the two different transportation modes. Since the two kinds of sediments produced by the two kinds of transportation movements may have different fractal characteristics；sedimentary rock and soil display the mixtures of the two kinds of sediments with different fractal characteristics. The traditional fractal model does not consider the larger error that may be produced when the traditional fractal model is employed in describing the size distribution of sedimentary rock and soil. On the assumption that common sedimentary rock and soil are mixtures of the two kinds of sediments with different fractal characteristics，an improved fractal model of size distribution is conducted；and the physical meaning of parameters of the model is validated too. Compared with traditional fractal model，the fractal dimension of suspend transportation deposit of the improved model varies greatly with different kinds of sedimentary rocks and soils. Finally，the improved model is adopted to analyze the differential slaking properties of red beds soft rock in Hunan Province.
