Numeric dynamics of population of Paeonia ludlowii, an endangered plant species mainly distributed in Nyingchi Prefecture of Tibet, were studied using the static life table, the survival curve, the fecundity schedule and the Leslie matrix model. Analytical results from the static life table and the survival curve reflect that Paeonia ludlowii underwent very strong environmental screening during its first 10 years and competitive self-thinning at the age between 20 to 25 years, the physiological life span of the species was about 20 years, and its maximum life span was about 35 years. The net reproductive rate, the intrinsic rate and the finite rate of increase of Paeonia ludlowii were relatively low, indicating that population of the species belongs to the type of decline. Results obtained by using the Leslie matrix model shows that both seedling numbers and total plant numbers of the species declined by about 30% during the past 20 years. The survival rate of Paeonia ludlowii population exhibits as the Deevey -I type, its mortality rate of individuals at the early stage was very high, and therefore it was short of young seedlings in its population. At present, the population is maintained mainly by shooting of itself. Thus, the possible factors leading to the species being in an endangering state are its biological characteristics and the disturbances from human activities.