Carbon(C) and nitrogen (N) stoichiometry are critical indicators of biogeochemical coupling in terrestrial ecosystems. Besides, the stoichiometric homoeostasis plays an important role in regulating structure, functioning and stability of ecosystems. So far, researches of C:N stoichiometry in plants were concentrated on aboveground leaves. Knowledge on belowground roots remains unclear. In this study, roots of 22 plant species were sampled in Nanji wetlands of Poyang Lake. Subsequently, C and N concentration were measured based on root orders. The results showed that the variation range was from 267.15 to 423.22 mg/g for root C, 2.22 to 31.05 mg/gfor root N and 2.27 to 71.78 for root C:N ratio, respectively. C, N, and C:N ratio of the first-order roots were significantly correlated with the second-root orders, but not with the third-order roots. C concentration and C:N ratio increased with root orders, whereas N concentration decreased with root orders. Hence, it is necessary to separate root orders for plants C and N stoichiometry researches in wetlands. Moreover, root orders, species and their interaction all significantly affected root C, N, and C:N ratio. Root C:N ratios were not significantly different between high floodplain meadow and low floodplain marsh, suggesting that root C:N stoichiometry was more constrained at community level than individual level in Nanji wetlands of Poyang Lake.