Ecologic patterns and community succession are generally controlled by hydrologic mechanisms, especially for plant distributions which are sensitive to habitat conditions. The hydrology characteristics of ecosystems mainly influenced plant ecological processes in water and salinity changes. In this paper, we analyzed the composition and characteristic of natural plant community, divided the plant community classes and discussed the effect of water and salinity gradients on plant species and community classes in Ejina Desert Oasis. The results demonstrated that Populus euphratica, Tamarix chinensis and Phragmites communis were the most important plant species that had the highest important values among forest, shrubs and herbaceous. Six plant community patterns were classified by cluster analysis in Ejina Desert Oasis. Species richness and species diversity were the highest near West River and East River channels of the core oasis area. The distributions of plant community were mainly influenced by the following factors: distance from river channel, groundwater level, soil water content, soil salinity and groundwater salinity. The water and salinity factors, which controlled the distributions of plant, were the main driving forces for ecosystem succession. The plant community succession is becoming toward the type of shrub + herb or low shrub with very drought-tolerant from the type of forest + shrub + herb with tall and high water consumption, when habitat conditions change from good to poor. The water gradients had more significant and more directed effect than salinity gradients on plant species and communities.