The desert-oasis ecotone is an ecological transitional zone between desert and oasis ecosystems, and it is also highly sensitive to climate change. The importance of the desert-oasis ecotone has received increasing attention in recent years. The changes in plant populations and in community dynamics due to environmental disturbances reflect the interaction mechanism between the ecotone and climate change, providing a foundation for understanding and predicting plant responses to climate change. Population structure reflects not only population dynamics and plant development, but also reflects the relationship among the population, its environment and each plant's position in the population; thus, comprehensive studies of population structure can reveal population size, survival conditions, and habitat suitability, and, when combined with analyses of ecological requirements, survival rates, and reproduction rates, also allow the evaluation of past population disturbances and predictions of future behavior. Thus, they are invaluable in understanding how populations adapt to environmental condition and will prove essential in protecting and regulating endangered plants. The shrub Calligonum mongolicum (Polygonaceae) is one of the most important sand-binding plants in the desert-oasis ecotone of the middle reaches of the Heihe River Basin in Gansu Province, China; it plays an important role in the stability of the desert-oasis ecotone. To elucidate the population structure and population dynamics of C. mongolicum, we surveyed and analyzed the size and structure of a natural C. mongolicum population in the field. Based on these data, we estimated the survival curve, mortality curve, and life expectancy of the plants, as well as other population parameters. Population dynamics were predicted by a time-sequence model. The aims of our study were to 1) provide references for the regulation and protection of C. mongolicum and 2) formulate strategies for enhancing its reproduction and restoring populations. The results showed that: 1) The age structure of the C. mongolicum population was a pyramid, with the size classes Ⅰ-Ⅲ comprising 89.98% of the total population, but there were fewer individuals in classes I and Ⅱ than in class Ⅲ. Using the quantization method of population dynamics, we found that the C. mongolicum population was of the growing type, with a dynamic index of population size structure of V_pi'=0.0233 under random disturbance, which showed that its population tend to be stable in this desert-oasis ecotone and that it was very sensitive to environmental disturbance. 2) The stationary life table of the C. mongolicum population indicated that the number of survivors, l, at age x years (l_x) decreased as size class increased; the observed life expectancies, e, at age x years (e_x) were highest in size classes I and Ⅱ then decreased. The survival curve of the C. mongolicum population showed that it approached a Deevey-Ⅱ type, and the mortality rate in different size classes was similar. 3) The time sequence model predicted that the number of individuals in size class IV would increase in the coming 2, 4, 6 and 8 age classes, but the numbers in size classes Ⅱ and Ⅲ would decrease. Therefore, if appropriate action is not taken to protect and foster these plants, C. mongolicum populations will inevitably decline from a lack of recruitment of young individuals. Therefore, we encourage appropriate vegetation restoration by humans and the protection of their habitat as crucial strategies to renew the natural C. mongolicum populations.