Abstract: 【Objective】We analyze the age structure and dynamic characteristics of Acer catalpifolium, a unique endangered species in China, reveal the relationship between A. catalpifolium populations and their environment, predict the patterns of population dynamics, explore its endangered mechanism, and propose protection and restoration strategies for wild populations.【Method】A. catalpifolium trees in Emeishan and Dujiangyan, Sichuan Province were studied by field investigation, the method of sample square survey was adopted. The sample area were divided into 1 to 4 samples square of 20 m × 20 m, and then each sample square was divided into 16 small squares of 5 m × 5 m. The A. catalpifolium in the sample square were investigated per wood, investigation content includes some growth factors such as the number of individuals, height of tree, DBH(diameter at breast height), and some habitat factors were recorded such as altitude, latitude, longitude, slope direction, slope, forest canopy density, soil type and vegetation community, the DBH of A. catalpifolium was used to represent age class to reflect the population structure, the DBH size of A. catalpifolium was divided into 11 diameter classes(Ⅰ—Ⅺ; D_DBH>50 cm is grade Ⅺ, and the interval of each stage is 5cm), the age class corresponds to the DBH class. The diameter class structure chart was drawn, time-specific life table of the population and important parameters(survival curve and mortality curve)were built and analyzed, the population dynamics were predicted by time series model.【Result】The populations of A. catalpifolium in Emeishan and Dujiangyan were significantly different, there are 105 individuals in Emeishan population and 81 individuals in Dujiangyan population, the age class structure of the population was complete. The diameter class structure of A. catalpifolium showed a spindle-shaped structure with a large proportion of middle age grade and a smaller proportion of young age grade and old age grade. The dynamic change index of population age structure of A. catalpifolium showed that the population age structure dynamic index under random disturbance(V_pi')were 0.011 6 and 0.004 2, respectively, both of which were close to 0. It was showed that the populations were converting from decay-type to decline-type structure. According to the life table, the early death rate of A. catalpifolium was higher than other age, the survival rate were decreasing with age class increased, and the selection effect of the environment was strong. The survival curve were tend to Deevey-Ⅱ, and the mortality was similar in each age level. The survival function analysis showed that the survival rate function S(t) of the two populations presented a monotone decreasing trend with the increase age level, while the cumulative mortality rate F(t) presented a monotone increasing trend, and the changes of the two function curves were complementary. The time series predicted that the number of saplings decreased with old trees increasing gradually. It may difficult to remain the stability of the population for a long time after more trees grow in the 2, 4, 6, 8 age groups in the future. If the seedlings in the population are difficult to supplement, and saplings are not sufficient, the population of A. catalpifolium will become a declining population after 4 years of age.【Conclusion】The biological characteristics and human interference may be the key factors which had made A. catalpifolium endanger, the protection of the population and habitat of A. catalpifolium should be strengthened, the existing adult individuals of A. catalpifolium should be protected, promote the germination of seeds and the renewal of seedlings, and prevent the destruction of habitat and ecosystem. In order to improve germination rate and seedling formation rate of A. catalpifolium seeds, promote seedling conversion rate of A. catalpifolium seeds, the biological characteristics and breeding of A. catalpifolium should be further studied. In addition, artificial cultivation and other measures should be taken to strengthen the protection of individuals and habitats of middle and small diameter A. catalpifolium population in the regeneration of natural forest, so as to promote the natural regeneration and recovery of A. catalpifolium population.