The theory of niche breadth has played an important role in the study of community composition and function, of the relationships among species, biodiversity, community succession and population evolution since Grinnell proposed that niche breadth was the minimum unit of a population. Yushan Island belongs to an archipelago of 13 islands and 41 reefs southeast of Xiangshan, in Zhejiang province. To determine the composition of the intertidal macroinvertebrate communities of Yushan Island, quantitative surveys were conducted according to the National Standard, GB/T 12763.6-2007, from March 2009 to January 2010. Eighty-five species of macrobenthos were identified, including 30 dominant species belonging to 24 families, seven classes and five phyla. Most organisms were arthropods or mollusks. Shannon-Wiener's Niche Breadth (NB) index and the Pianka's Niche Overlap index were used to compare dominant species. NB was significantly different among species. Septifer virgatus, Serpulorbis imbricata, Modiolus modiolus, Tetraclita japonica, T. squamosa and Pilumnus minutus had large niche breadths (NB>1.00), while Littorina brevicula, Crepidula gravispinosa and Ophiura kinbergi had narrow niche breadths. The adaptabilities of the most dominant species to environmental conditions (NB >1.00) were higher than for other species (NB<1.00). The abundances of individuals of species restricted to conditions located only within a narrow intertidal section or to only certain seasons, for example L. brevicula, was higher, but the niche breadth of these species was not larger than the other species in the same restricted habitats. Thus niche breadth was related to habitat. Niche overlaps, which varied from 0 to 0.97, were impacted significantly by niche breadth and relative abundance. Tetraclita japonica and T. squamosa had a niche overlap close to 0.97. Thus it is likely that when these two species are located in the same portion of the middle intertidal zone, there is competition for substrate. Crepidula gravispinosa and Ophiura kinbergi were found in association with Mytilus coruscus; Corophium acherusicum and Clianella japonica, and both occupied burrows produced by mollusca. Acanthochiton rubrolineatus and Thais luteostoma also typically cohabited the same area. It is likely that space competition among the dominant species was intense since the niche overlap exceeded 0.9. Niche overlaps occurred between species with both low niche breadth and high niche breadth. Niche overlaps of zero indicated that the species did not inhabit that environmental site. Using hierarchical clustering with between-group linkage and non-metric multidimensional scaling, the 30 dominant species were classified into three groups: rare, common and special species. Spatial distribution, niche overlap, functional feeding differences and habitat differences were the principle strategies used by each species to reduce competition.