Based on field investigation and indoor measurement, the composition of aquatic plants and the niche characteristics of dominant species in wetlands of the Yellow River Delta were studied using Levins and Pianka formulas. A total of 34 species, belonging to 16 families and 26 genera were observed in the investigation plots. Species composition and dominant community types were significantly different among investigation regions. Higher species numbers and richer community types were observed in the regions with longer formation time. For emergent plants, Phragmites australis (0905) and Scirpus triqueter (0.127) had the maximum and the minimum niche breadths respectively. For submerged macrophytes, Chara sp. (0.783), Myriophyllum spicatum (0.673), Ruppia maritime (0.669) and Najas minor (0.640) had relatively higher niche breadths and Ceratophyllum demersum had the minimum niche breadth (only 0.100). The niche overlap values among Potamogeton pectinatus, Najas marina and Vallisneria natans and the value between Potamogeton malaianus and Potamogeton cripus were relatively higher, indicating that they had similar capacity to acclimate to the environment. Species niche breadth was significantly correlated with its distribution range and salt\|tolerance ability. Therefore, it can be concluded that salt contents in the soil and water are the key factors determining the niche differentiation among aquatic plants in the Yellow River Delta.