Abstract: A static life chart of the Pinus massoniana population in the southern suburb of Nanjing was plotted through collecting statistics of ages of the trees in the population. Results show that the population is of a declining type in age structure and its survival curve is a convex one of Deevey-A type, while its mortality rate and disappearance rate varies similarly reaching as high as 0.625 and 0.981 in the eleventh age class(47-49 a) respectively. Calculation of the Hegyi competition index indicates that intraspecific competition is the main cause leading to decline of the population, with index amounting to 85.8% of the total competition index. The average intraspecific single-tree competition index of the population is 1.71, while its interspecific competition amounts only to 14.2% of the total. SPSS nonlinear regression shows that LIN Zhenshan's intraspecific competition model can be used to fit the declining tendency of the P. massoniana population, with high goodness and determination coefficient being 0.759. The inherent natality of the P. massoniana population is 0.105, and the highest environmental capacity for P. massoniana in this area is 31(400 m²)^-1. Model stability analysis indicates that though the P. massoniana population in the southern suburb of Nanjing is declining, it won't extinct in this area, and will remain to be the dominant species in the community for a long time in future, however, its population density will keep on declining and level off at 9.396(400 m²)^-1.