The composition and distribution characteristics of vegetation play a vital role in the development and stability of the sandbars. Operation of the Three Gorges Reservoir has changed the hydrological and sediment transport regimes in the downstream of the dam, causing a significant gradient on the sandbar habitats along the flooding durations. To clarify the composition, distribution, and structural characteristics of vegetation in the sandbar is fundamental for understanding the roles of vegetation in stabilizing the sandbar. In addition, they provide key information to clarify the relationship between the Three Gorges Project and the ecological and environmental problems in the middle and lower reaches. In this study, we selected the first sandbar, the Taipingkou Middle bar in the upper Jingjiang river section, and used the equidistant systematic sampling plots to investigate the vegetation composition and distribution characteristics. Based on the elevation information of plots and the water level data over the years, we set the plots at 5 flooding gradients levels by the flooding days in a flooding cycle:20-40 d, 40-60 d, 60-80 d, 80-100 d, and over 100 d. Statistical methods, such as importance value, species diversity index, functional diversity index and functional traits analysis, were used to analyze the species composition, diversity and functional traits of communities under different flooding duration days. The results showed that the vegetation composition was dominated by herbaceous plants, and the small shrubs Salix triandroides were sparsely distributed. A total of 39 species, belonging to 21 families and 39 genera, were recorded and the main dominant families were Poaceae and Compositae. The species composition of habitats under intermediate level (20-40 d) and maximum flooding intensity (100+ d) condition is significantly different with that found in other flooded gradients. Under the intermediate flooding intensity, Hemarthria sibirica and Equisetum ramosissimum are the main dominant species, and Phalaris arundinacea is the main dominant species under the maximum flooding intensity. Along the flooding gradient, species diversity is significantly varied. Species richness is low in both intermediate and maximum flooding intensity habitats, but the highest species diversity in the intermediate flooding condition habitats and the lowest in the maximum strong flooding intensity habitats. Basically, the trend of functional diversity index keeps same with biodiversity index, while the functional diversity index under maximum flooding conditions is not representative. As increasing of intensity of flooding stress, the vegetation tends to show the functional traits with flowering and fruit stage under the outcrop stage, while plant height reduction, fibrous root system and vegetative reproduction also show difference. The community structure and the functional traits of the sandbar plants showed obvious gradient change with the flooding gradient. The results show that the gradient change of flooding duration is an important driver shaping sandbar plant community, and provides an important basis for further research on the dynamic succession of sandbar plant community and vegetation succession mechanism of sandbar, and clarifying the ecological environment changes under the influence of dams.