Abstract: The microstructure fractal of sliding zone soil of Suoertou landslide is studied. The sliding zone soil is tested for physical-mechanical properties through the laboratory tests, then by use of the scan electronic microscope technique (SEM), the image-processing-analysis and computer-vision technique, the microstructure fractal parameters of soil pores are extracted based on the fractal geometry and the perimeter-area method. The influences of the threshold and magnification on the quantitative results of soil microstructure are investigated, and the standard of image processing is determined according to them. The results show that the sliding zone soil of Suoertou landslide is marked by fractal. Finally the relationship among fractal dimension, void ratio and shear strength of soil is expounded, indicating that the shear strength increases and the void ratio decreases with the increase of the fractal dimension, and vice versa. It provides a reference basis for forecasting the mechanical behaviors of soil by its microstructure fractal parameters.