Soil structure is the material base of soil fertility and has an important significance in soil fertility.In order to study the relationships between soil particles and the fertility of black soil in northeast China,fractal dimensions of soil inorganic particles and complex were calculated by the particles fractal theory.The distribution characteristics of black soils in northeast China and its relationships with soil fertility were analyzed as well.The results showed that the fractal dimensions of black soil inorganic particles in northeast China were 2.80-2.90,significantly correlated with the entire size fraction.The fractal dimensions of complex were 2.66-2.93,correlated positively with clay and negatively with silt complexes.The regression equation（y=88.18x－60.73x2+10.57x3）between the fractal dimension of inorganic particles and complex showed that inorganic particles and complex organic could decrease the fractal dimension,and might decrease soil complex degree because of low temperature and increase the fractal dimension of soil.Association analysis between the fractal dimension of soil particles and the fertility confirmed that inorganic particles and complex organic could increase soil nutrients storage capability,and might release nutrients gradually in the process of mineralization.It can be concluded that the fractal theory could be taken as a quantitative indicator explaining the mechanisms of inorganic compound particles and soil structure and indicating fertility characteristics under the conditions of the fractal dimension of soil.