Abstract: Taking a engineering site in Xiamen for example, the distributed granularity of the weathered residual granite is studied. The result shows that it has the character of fractal dimension, the higher degree of weathering, the bigger fractal dimension and the fractal dimension could reflect the grain thickness and the distributed gradation. In the end, the fractal dimension of granularity could be used to be as an index to plot the weathered strip and evaluate mechanical property and permeability.