Abstract: Applying the fractal theory to analyze the microporous structural features in great overburden clay from the southwest regions of Shandong Province.The study shows that in this area the total porosity distribution and pore size of deep clay at the double logarithmic coordinates have a good linear relationship,and cross-correlation is greater than 90%.The authors indicate that the value of fractal dimension is a comprehensive index that can really reflect pore characters.It is soil porosity quantitative description of the effective ways.The pore aperture of this clay is greater than 1 μm,and its fractal dimension in value ranges from 2.5 to 2.6.The study also obtained that the 2 μm pore diameter of deep clay is a critical value for the porosity nature changing in this area.