Water depth is a key factor that affects the growth and reproduction of wetland vegetation. Different types of wetland vegetation respond to flooding in different ways. It has been known that the hydrological regime is highly dynamic in the Poyang Lake; however, how the wetland vegetation population and community changes along with the varying water depth is still not well understood. To explore the underlying influence of water depth on the growth of wetland vegetation, a control experiment was carried out to determine the growth and reproduction of three dominant wetland plants (Carex cinerascens, Miscanthus lutarioriparius,and Phalaris arundinacea) in the Poyang Lake wetland under different water depths (0, 0.5, 1 m, and 2 m). The results showed that 1) water depth had the most significant influence on the total biomass of C. cinerascens, and the biomass of C. cinerascens was concentrated in the underground parts during the flooding; the biomass of M. lutarioriparius gradually decreased as the water depth increased. On the other hand, water depth had no significant impact on the biomass of P. arundinacea (P>0.05). In terms of biomass, P. arundinacea had greater adaptability to flooding than the other two plants. 2) Plant height of C. cinerascens was significantly reduced under flooding conditions. Plant height of M. lutarioriparius was reduced only under a water depth of 2 m.These findings suggest that in low flow years, the decreased water level may help M. lutarioriparius to migrate to a lower elevation. 3) The water depth had no obvious impact on the ramets of C. cinerascens (P>0.05). However, the number of ramets of P. arundinacea was greatest when grown under a water depth of 2 m. These results demonstrate that in high flow years, the elevated water level has less impact on the reproduction of P. arundinacea. Above all, in a wetland ecosystem with periodic flooding, the depth has a significant impact on the growth and reproduction of wetland vegetation during the flooding period. Our results provide important clues for further study of the survival and distribution of wetland vegetation.