The present study investigated differences in the C, N, and P ecological stoichiometric characteristics of Taxodium ascendens Brongn. and soil in the water-level fluctuation zone of the Three Gorges Reservoir (TGR) region. The C, N, and P contents and stoichiometry in different parts (branches, leaves, and roots) of T. ascendens and in the soil in Zhong County under three submergence treatments (Deep Submergence, DS; Moderate Submergence, MS; and Shallow Submergence, SS) were measured and analyzed in July 2018. (1) The height, canopy, basal diameter, and DBH of T. ascendens were all inhibited by increasing flooding time and intensity, whereas growth was maintained, possibly due to the tree's stable stoichiometric ratio. (2) Submergence treatment had no significant effect on the C, N, or P contents or ratios of the branches or leaves (P>0.05), and the N and P contents decreased as follows: leaves > roots > branches > soils, under each submergence treatment. The C, N, and P content of other organs were significantly greater than those in the soils, except for the P content of the branches (P<0.05). (3) The N/P ratio of each T. ascendens organ was much lower than the threshold (<14), which suggested that the growth of T. ascendens is more severely restricted by N. (4) The homeostasis of the C, N, and P contents of T. ascendens and soil decreased as follows: P > C > N, and the homeostasis ratios decreased as follows: C/N > N/P > C/P. The homeostasis of C, N, and P in the aboveground parts (branches and leaves) and their ratios were much higher than that in underground parts (roots). (5) Redundancy analysis (RDA) indicated that the ecological stoichiometry and growth indicators of T. ascendens were closely related to soil properties. This work demonstrates that T. ascendens is able to grow well and to effectively maintain the stoichiometry balance in response to different flooding strengths that result from hydrological changes in the water-level fluctuation zone of the TGR region. In other words, T. ascendens is a potentially promising tree species for vegetation restoration and reconstruction in the water-level fluctuation zone of the TGR region.