Abstract:Masson pine (Pinus massoniana) is one of the pioneer species of the subtropic forest succession and of all the secondary succession stages on, the Jinyun Mountain,which is situated in the northwest of Beipei district Chongqing city, Sichuan Province (29˚50′N,106˚26′E). The study on the quantitative dynamics of Masson pine population is of great significance for studying the forest communities and ecosystems in subtropic China.The use of the plot-chronosequence provides a short-cut method for studying the population dynamics of long-lived plant species. Bfore the age of seven, the density of a Masson pine population in the mountain increases and the rate of its growth decreases with the passage of time. And beyond that age, the density decreases and the rate of growth increases with the passage of time. The density would continue to decreases even after 30 years, but the rate of growth would increase markedly with the lapse of time.In the period between shrub-grassland and Masson pine forest, the dynamics of population biomass shows a logistic growth, i.e. where A is the population’s age in years Bp is estimation of the population biomass in t.ha-1. In the period between the coniferous broad-leaved mixed forest and the evergreen broadleaved forest, the population biomass decreases with the time passed. The relationship between the populational density and the mean plant biomass during the self-thinning accords .with t he-3/2 thinning power law and can be described as,where, Bi is mean plant biomass in kg, D, populational density in trees.ha-1. The obvious factor resulting in the quantitative dynamics of Masson pine population at the mountain is the self-thin-ning caused by intraspcoific competition and the alien-thinning by interspecific competition for the light resource in the stand.