Syringa pinnatifolia Hemsl. is a unique rare and endangered species in China. In this study, surveys on the natural population of S. pinnatifolia in the Gangou Preserve in the Helan Mountain and Xiangshan in Zhongwei city were conducted for the first time. Characteristics of population structure were described by establishing a static life table and drawing a population survival curve. Their future development trends were researched quantificationally by population dynamic prediction and time series analysis. The results showed that the Xiangshan population fit the growing type, and the Helan Mountain population fit the declining type. Both populations were sensitive to external interference. The population development of S. pinnatifolia was primarily maintained by middle-and old-aged individuals, with a lack of seedlings to different degrees. The population survival curves tended to be the Deevey-Ⅱ type. Mortality and risk curves both showed that the mortality at each age level rose in a fluctuating manner as age increased, and the range of fluctuation in the Xiangshan population was the most significant. Survival analysis also showed that Xiangshan population entered the decline phase earlier than the Helan Mountain population. Combined with the habitat conditions, the Helan Mountain region was more suitable for the survival of S. pinnatifolia. Dynamic indexes and the results of time series analyses indicated that the population of S. pinnatifolia had the following dynamic characteristics:early stage, declining; middle stage, stability; and late stage, recession. The lack of young individuals was one of the main reasons for its endangerment. Consequently, suggestions are put forward based on the closure of hillsides to facilitate afforestation, the strengthening of research on highly efficient breeding technology of S. pinnatifolia, and the implantation of artificial rearing measures to ensure the normal development of its population.