Abstract: Self-thinning of Spruce population on sandy land was investigated with population density regulative law. Population density dynamical process was simulated as well. Owing to plastic growth, the relations among average DBH, average dry weight of individual plants and density of population varied among spruce populations in various types of forest. Main factors involved in population regulation were analysed with principal components analysis. The results are as follows: main factors which affect self-thinning process of spruce population were the following 7 factors: orientation of slope, type of community, position of slope, average water content of soil, elevation, average unit weight of soil, and density of coniferous leaves. Mechnism of self-thinning and its applications in population density management which is very significant for spruce population management were also discussed.