Abstract: The selecting-density experiment of Cyclpbalanopsis elevaticostata plantation was carried out to solve the production decrease and soil degradation due to conifer problem and continuous planting in east Fujian mountainous area. The fractal theory was used to study the soil structure and physicochemical properties of different densities including 2400, 3000, 3600 and 4500 tree/hm2 of Cyclpbalanopsis elevaticostata plantation and barren mountainous area. The results showed that the soil fractal dimension had significant regression relationships with soil water stable aggregate, soil aggregate contents, ratio of structure damage and physicochemical properties. The soil fractal dimension showed a positive linear correlation with the content of soil particle ＞0.25 mm and a negative correlation with the ratio of structure damage. The fractal dimension of soil aggregate structure in different densities showed an order as: barren mountainous area＞4050 tree/hm2＞3600 tree/hm2＞2400 tree/hm2＞3000 tree/hm2. The above results indicated that the fractal dimension was able to characterizing soil fertility. The density of 3000 tree/hm2 of Cyclpbalanopsis elevaticostata plantation was the best in structural stability and fertility status. Application of the fractal theory to the research of forest soil fertility provided a new idea for forest assessment.