Soil salinity changes caused by altering hydrological regimes can directly affect the distribution and succession of vegetation in desert-wetland ecosystem. By investigating the vegetation in 171 quadrats at 57 study sites, soil pH and soil conductivity, which were regarded as the key soil factors determining species distribution, were selected and divided into 6 levels to explore the niches of 15 dominant species in Dunhuang Xihu wetland ecosystems. This study aimed to discuss the ability of different species in resource utilization and ecological space occupation, which has important implications in maintaining and conserving the biodiversity in this desert-wetland ecosystems. Results showed that: (1) along the soil pH and conductivity gradient, both Tamarix ramosissima and Phragmites australis had highest importance values and largest niche width, which indicated these two species had stronger adaptation ability and can made better use of resources. As the generalist species, they seemed to play important roles in plant communities. Following them, Alhagi sparsifolia, Populus euphratica and Lycium ruthenicum also had strong adaptability to environmental factors. (2) The niche width of dominant species were overall similar but with differences along the two soil environmental gradients, e.g., the niche width of Nitraria sphaerocarpa and Calligonum mongolicum along soil pH gradient were larger than those along soil conductivity gradient, while Kalidium cuspidatum and Tamarix austromongolica had larger niche width along soil conductivity gradient, and showed stronger salt tolerance, thus the utilizing ability and adaptation of these species to different soil factors were not identical. (3) Most species' niche overlap were minor, 58.10% species were lower than 0.5 across the two resource axes. It suggested that the species niches had obvious differentiation along soil pH and soil conductivity gradients. (4) There were negative (but not significant) relationships among 15 dominant species, which indicated that the species were competitive, but the competition intensity was low and the community stability was relatively weak.