This paper studied the distribution and feature of soil particles and water-stable aggregates, and the distribution of fractal dimension of particles and water-stable aggregates under different karst ecosystems. Results showed that the fractal dimension of particles appeared high significant positive correlation with the contents of clay and physical clay, but high significant negative correlation with sand content. The fractal dimension of water-stable aggregates exhibited significant negative correlation with contents of >0.25mm water-stable aggregates, soil organic matter and cation exchange capacity, but high significant positive correlation with the percentage of structural damage, soil bulk density and percentage of bare rock in karst ecosystem. Soil bulk density increased after the breakage or farming of secondary forestland, at the same time, contents of clay, soil organic matter and soil water-stable aggregates all exhibited decreasing trends. There existed significant quantitative correlation between soil fractal dimension and soil properties. Fractal dimensions of particles and aggregates exhibited identical function in disclosing soil properties, soil quality and soil degradation degree. So fractal dimension can be used as an effective method in evaluating soil quality and the degree of karst rock desertification.