Abstract: Fractal geometry is a method of discovering the rules such as self-similarity of irregular curves, the self-inverse of irregular figures, the self-squaring of fractal translations, the self-affine of fractal groups and so on. If it applies on the research jobs of micro-structural fractal features, some key-techniques of soil microstructure mechanic would soon be solved. To use the fractal geometry in micro-analysis of saturation soft soil, the most important thing is to get microstructure fractal features parameters such as the fractal dimension of grains, the fractal dimension of holes. With the liquid nitrogen refrigeration sample-made technique, the scan electronic microscope technique （SEM） and the image-processing-analysis and computer-vision technique，46 group samples’ microstructure fractal features parameters of saturation soft soil which withdraw from Guangdong Scientific Center are extracted. By adopting variable gradually linearization regress analyses, the relationship between the fractal features and the porosity are discussed.

Key words: saturation soft soil, microstructure, fractal features, fractal dimension