Hydrological rhythm is a main driver for the succession of riparian plant communities in fluctuating zones, and the water level regulation of "winter storage and summer discharge" in the Three Gorges Reservoir area is not conducive to the survival of the terrestrial plant communities in the original riparian zone. To reveal the spatial and temporal patterns of the species diversity and distribution of vegetation in the fluctuation zone of the Three Gorges Reservoir after long-term fluctuation in water levels, we conducted a resetting investigation on the natural distribution and species diversity of vegetation in the fluctuation zone in September 2016, based on field survey data from the typical regional fixed plots in the fluctuating zone set in 2008. Statistical methods, such as importance value, diversity index, and LSD test, were used to thoroughly discuss the species composition, community diversity, and life form. The results showed that the regional vegetation type was dominated by annual and perennial herbaceous plants, and a total of 49 species of herbs, belonging to 22 families and 40 genera, were found and identified. The dominant families were Gramineae with six genera and six species, Asteraceae with nine genera and nine species, Polygonaceae with three genera and one species, and Euphorbiaceae with six species in five genera. The floristic characteristics were of single species and genera. Along with the altitude, the species diversity presented a "single peak" distribution pattern, and plant species diversity in the fluctuation zone was the highest at the middle altitude (155-165 m). The trend simulation between the altitude and the dominant species diversity index (Shannon-weiner index、pielou index、simpson index and richness index)showed a power exponential relationship, with fitted coefficients of 0.834, 0.824, 0.817, and 0.808, respectively. Depending on the structure of the environmental resources, the species showed a specific R survival strategy at different altitudes. In addition, nine types of life forms were found in this zone. With an increase in altitude, annual herbaceous plants occupied a great dominant position, but the life type of the plants in the reservoir became more diverse. The species of other plant living types, such as vines, shrubs, and deciduous trees, are gradually increasing. These findings would be of great reference value to the future improvement of species diversity and maintenance of vegetation in the fluctuating zone.