Abstract: Based on the plant ecological survey on main vegetation communities in the Yellow River Delta, the population niche breadth and overlap of succession series of both terrestrial and aquatic vegetation were analyzed. The results show that terrestrial vegetation succession occurs in the following stages: Suaeda salsa community → S. glauca + Tamarix chinensis community → T. chinensis community → Imperata cylindrical community. The dominant species in each succession stage exhibits a large niche breadth and importantly influences on the community. Niche breadth of S. salsa in S. salsa community is 9.99, that of S. glauca in S. glauca+T. chinensis community is 9.72, it is 9.20 for T. chinensis in T. chinensis community, and is 9.31 for I. cylindrical in I. cylindrical community. The succession stages for aquatic vegetation are: Potamogeton spp+Ceratophyllum demersum community (immersed vegetation) → Lemna minor+Hydrocharis dubia community (floating vegetation) → Phragmites communis +Typha angustifolia community (emergent aquatic vegetation) → Salix integra+ P. communis community (hygrophyte vegetation). Niche breadth of Potamogeton spp in immersed vegetation is 8.62, that of L. minor in floating vegetation is 9.23, it is 8.59 for P. communis in emergent aquatic vegetation, and 7.45 for S. integra in hygrophyte vegetation. Niche breadth well corresponds to the role of population in the communities, which changes during succession series in response to population dynamics. The niche overlap is lower among populations in different succession stages, and higher among population inner the same succession stage.