In this study, the population distribution patterns and growing status of Triarrhena lutarioriparia along a gentle elevation gradient were analyzed based on an investigation of the fixed quadrat plot and a method of variance to mean ratio in a typical beach of Lake Dongting wetlands. The results indicated that (1) soil moisture content was significantly higher in the low altitude areas than in the high altitude areas. Soil particle composition of low altitude areas was significantly different from that of high altitude areas. Soil pH was all alkaline. There was also no significant difference in soil total organic carbon, total nitrogen, ammonium nitrogen content and pH, while soil nitrate nitrogen content in low altitude areas was significantly lower than that in the high altitude areas. Soil total phosphorus content was significantly lower in high altitude than that in low altitude, while available phosphorus, total potassium and available potassium showed opposite patterns. (2) The population distribution patterns of T. lutarioriparia in both low and high altitude areas were all changed from a uniform distribution to an aggregated pattern, while the aggregation intensity was greater in the low altitude areas. (3) The biomass of T. lutarioriparia accumulated rapidly along with the time going, which was significantly lower in the low altitude areas than in the high areas. Density and basal diameter of T. lutarioriparia increased significantly along with the time going, which were higher in the low altitude areas than in the high altitude areas. These results indicated that the soil moisture content had a significant influence on the population distribution patterns and the status of T. lutarioriparia growing. Therefore, moderate regulating of water level and increasing soil moisture content may be adaptive to control the invasion of T. lutarioriparia into the Carex community.