Abstract: Phalaris Arundinacea is a typical dominant plant population in the beach wetland of the Poyang Lake, which is of great significance for the maintenance of wetland ecology and environment. Taking P. Arundinacea as the research object, field surveys and statistical analysis methods were used to study the relationship between natural distribution characteristics and influential factors (soil moisture status and altitude) of the population of P. Arundinacea. The results showed that: (1) According to the Gaussian regression equation, P. Arundinacea was distributed at elevation from 9.85 to 18.11m, and the optimal elevation is from 12.13 to 15.84m. (2) As dominant specie, the population of P. Arundinacea appeared more frequently at elevation from 12 to 15m, and showed greater average coverage and average height at elevation from 14 to 18m. (3) As companion specie, the population of P. Arundinacea appeared more frequently at elevation from 13 to 15m, and showed greater average coverage at elevation from 15 to 16m and 18m; its average height was larger at elevation from 14 to 15m and 17m. (4) Soil moisture status had a significant effect on the natural distribution of P. Arundinacea population. The frequency of P. Arundinacea population decreased with the increase of soil humidity, and it grew best in wet environment. P. Arundinacea's appearance frequency as dominant specie decreased in the soil moisture status of dry, slightly moist, moist, wet, damp. While its appearance frequency as companion specie decreased in the soil moisture status of dry, slightly moist, moist, damp, wet.