Keywords: 
• Hainan island /
• Cyperaceae /
• Distribution characteristics

Abstract: A field survey was made to investigate Cyperaceae plant resources in 18 counties or cities of Hainan Island,China during the years from 2010 through 2016. This survey covered tropical tussock grassland in the low mountains and hills,mountainous tropical sussock grassland,tropical shrub-tussock grassland,hot-dry savanna shub-tussock grassland,low wetland meadow grassland,coastal low-lying saline-alkaline grassland,and farmland interval grassland. Sample-line method was used for the survey to record all the plants of this plant family along the designed line,and dotted survey was also made to observe the specificity of the subgenera or species of the plant family to their living environment. The distribution characteristics of the plants were entered into record in detail and the classified. The survey found there were 164 species. 6 subspecies and 9 varietas under 24 genera distributed in these areas under survey. The distribution characteristics of the Cyperaceae plants in different types of grasslands in Hainan were analyzed in terms of ecological environment,community structure and species composition. The analysis showed that the Cyperaceae plants are divided into five major ecological types based on their distribution: Ⅰ. Humidogene and paludous type; Ⅱ. High canopy density undergrowth type;Ⅲ.Sunny slope shrub,rocky crevice or mountainous shrub grassland type; Ⅳ. Coastal sandy grassland,salt marsh and sandy seabeaches type;Ⅴ. Xerophytic cosmopolitan type.