Population is not only the fundamental unit of a species for existence, adaptation, and evolution, but is also the link among individuals, communities, and ecosystems. Analysis of plant population structures can reflect the current state of populations, and help to reveal future population dynamics. In this paper, the population structure and dynamics of four mangrove species (Kandelia obovata, Aegiceras corniculatum, Avicennia marina, and Bruguiera gymnorrhiza) in the Beilun Estuary National Natural Reserve, Guangxi, were analyzed. This study illuminates the structural characteristics of populations and communities, as well as potential mechanisms driving the population dynamics of mangrove species, and provides a fundamental understanding and scientific basis for the protection and restoration of mangrove ecosystems in Guangxi, southern China. Using survey data from 12 permanent plots (each 20 m×20 m), in this study we analyzed the height class, size class, static life tables, survival curves, and time sequences to describe and predict the population structure and dynamics of four mangrove species. Seven aggregation intensity indexes, including mean crowding index, clumping index, patchiness index, etc., were applied to analyze the spatial distribution pattern of mangrove plants with different size classes. The height structure and size structure analyses indicated that seedlings and saplings of B. gymnorrhiza and K. obovata were relatively abundant, and also that their populations showed robust regeneration. The regeneration of A. corniculatum was hindered to some extent, and there were fewer adult plants, although the quantity of seedlings and the overall population were relatively stable. There were fewer individuals and no seedlings in the A. marina population, which showed poor regeneration and an obvious decline. The static life table analysis showed that the survival of different age classes of the four mangrove plant species differed greatly, and that the survival and life expectancy gradually decreased with increasing age. The survival curve analysis suggested that A. marina showed a Deevey type I curve, and all individuals reached the average physiological life expectancy. B. gymnorrhiza and K. obovata showed Deevey type Ⅱ curves, and individuals of different age classes had relatively consistent death rates. The survival curve of A. corniculatum fell between the Deevey type I and the Deevey type Ⅱ curves, and while the death rates of young age classes were relatively high, they gradually stabilized after reaching middle age. Through time sequence analysis, it was predicted that the population of A. marina would decrease; the number of young individuals of A. corniculatum would decrease and that of adult individuals would increase, and the population size in the future would display a stable trend with a slight decline; and the number of young individuals of B. gymnorrhiza and K. obovata would increase, and the population size within different age classes would regenerate well; hence, their future population sizes are predicted to increase. The calculations of seven aggregation intensity indexes demonstrated that populations of different age classes of the four mangrove plant species mainly exhibited clumped distributions, and the aggregation intensity always tended to decrease with increasing age. The population dynamics of the four mangrove species and succession stages of the mangrove communities were closely related. The population of the pioneer plant, A. marina, was in a stage of relatively rapid depression, and the population of A. corniculatum, typical of early and middle succession stages, was stable with a slight decline. The populations of B. gymnorrhiza and K. obovata, typical of middle and late succession stages, displayed growth of various degrees. These results suggested that the mangrove communities investigated in this study were in the middle stage of succession, and that A. marina and the association of A. marina and A. corniculatum will gradually give way to an association dominated by B. gymnorrhiza. The population dynamics of mangrove plants were regulated by multiple factors such as habitat condition, intra-and inter-species competition, and insect pests. The clumped distribution of the four mangrove plants at different age classes was closely related to their reproduction modes and habitat conditions. The gradual decrease of aggregation intensity with increasing age might be caused by self-thinning, or thinning effects as a result of intensified intra-or inter-species interactions.