In recent years, ecologists have experienced an increased awareness of the importance of plant-environment interactions. Studies have demonstrated that spatial ecosystem heterogeneity and availability of resources influence plant growth. Understanding the ecological response characteristics of plants and environmental laws influencing arid land vegetation in different water-salt environments should be quite valuable to scientists. To better understand the ecological characteristics of plants and factors that potentially control them such as water availability and salinity in arid regions, we conducted a study in Phragmites australis in dry habitats of the Yutian Oasis along the Keriya River, in the southern marginal zones of the Tarim Basin, Xinjiang, China. Using previously collected observational data related to water-salt distribution laws and the natural water-salt gradient caused by distance from the river, four sample regions were established parallel to the river from east to west, extending from the river to the desert. We analyzed the patterns and correlations of ecological characteristics of Phragmites australis and water-salt indicators in the field, using traditional statistics and redundancy analysis (RDA) in combination with CANOCO software (version 4.5). The statistical analysis revealed that plant ground cover was as low as less than 10%; the belowground biomass was greater than aboveground because of the way desert vegetation adapted to the arid environment. The sampled region was severely dry and salinated; soil moisture content was low, with a mean value of 7.22%. The average depth to ground water was 4.23m and soil salt content reached as high as 18.24g/kg. Phragmites australis has a high tolerance to aridity and salt stress; the average plant height, coverage and aboveground biomass decreased gradually while the belowground biomass increased as distance from the river to the desert increased; there were also concurrent and expected gradient changes in water-salt indicators. Redundancy analysis showed that water was the key environmental factor influencing the growth of Phragmites australis. A significant correlation was found between ground water depth/soil moisture and the ecological characteristics of Phragmites australis including plant height, coverage, biomass; the sodium adsorption ratio (SAR)/total salt correlation with ecological characteristics was less significant while other indicators had no significant correlation with the plant's ecological characteristics. The importance of water-salt indicators to ecological characteristics of Phragmites australis could be arranged as ground water depth > soil moisture > SAR > total salt > HCO₃^- > pH > Cl^-/SO₄^2-. The results suggest that water has greater impact on Phragmites australis than salt, because water limits the plant's survival, growth and reproduction. When a plant is affected by an arid continental climate for long periods, the plant is usually influenced by both water and salt. Any study of Phragmites australis analyzing the effects of different water or soil salinity conditions independently would be fatally flawed; but must be considered together. Our study shows that redundancy analysis of ordination methods can be beneficially used in research into the relationship between plants and environmental factors; when combined with traditional statistics, the two methods can provide comprehensive information. The redundancy analysis can effectively reveal relationships between ecological characteristics of plants and water-salt indicators. The characteristics of Phragmites australis deserve more research, especially research related to the microscopic physiological effects of water-salt interaction.