Groundwater depth is important to wetland vegetation during non-inundation. However, the relationship between groundwater and wetland plants is still scarce. In this study, we investigated the effects of groundwater depth on the growth of Carex cinerascens, one of the dominant species in the Lake Poyang wetland based on controlled experiments. The experiment includes five groundwater depth treatments (10, 20, 40, 80 and 120 cm). Morphological and physiological characteristics of C. cinerascens as well as aboveground biomass were monitored. The results showed that the plant height, leaf length and aboveground biomass decreased with increasing groundwater depth. The biomass in 10 cm treatment (0.371±0.017 g) is 4.4 times of that in 120 cm treatment (0.084±0.004 g). The groundwater depth has significant effect on the enzyme activities, proline and chlorophyll. The proline content increased from 6.29±0.70 μg/g in 10 cm treatment to 8.54±1.37 μg/g in 120 cm treatment. These physiological differences among treatments suggested C. cinerascens would encounter some drought stress along with increased groundwater depth. All the results indicated areas with groundwater depth of less than 20 cm were suitable for C. cinerascens growth, but the growth of C. cinerascens would be impeded when the groundwater depth was below 80 cm.