Abstract: Based on field investigation and related literature, the composition of species, floral characteristics and spatial distribution characteristics of seed plants in Zhoushan were studied. Results showed that the study area had a total of 1372 species of wild seed plants, belonging to 627 genera and 141 families. The seed plant flora were found in many small families and genera, the major life form was herbaceous, the geographical components were widely varied, and seashore plants were abundant, though there were relatively fewer protected plants. The distribution of species richness and density was very uneven in the ten typical islands. Generally, the southern islands had higher species richness and species density than the northern islands. Of the eight major forest community types, Machilus thunbergii forest had the highest species richness in the arbor layer, Cinnamomum camphora forest had the highest species richness in the shrub layer, and Eurya emarginata bush had the highest species richness in the grass layer. Species richness, Simpson index and Shannon-Weaver index showed the characteristics of shrub layer > arbor layer > grass layer. The Pielou index had no significant variation in the arbor communities, but showed the characteristic of grass layer > shrub layer in the bush communities. Based on our investigation and analysis of species diversity of seed plants in Zhoushan, material for research on and protection of wild plant resources in the Zhoushan islands were accumulated, and a theoretical basis for the development and utilization of plant resources was provided.