Abstract: The fatty acid composition has important reference value for understanding the fatty acid resources of mangrove plants. The nutritional relationship within the mangrove ecosystem, the structure of food web and the adaptation of mangrove plants to habitat. In this study, composition and relative content of fatty acids in leaves of 7 mangrove species were analyzed, they were Rhizophora stylosa, Sonneratia alba, Xylocarpus granatum, Ceriops tagal, Lumnitzera racemosa, Bruguiera gymnorrhiza andRhizophora apiculata collected from Tielugang Bay in Sanya City and Qinglangang Bay in Wenchang City, Hainan, China. As results, a total of 25 species of fatty acids were recorded, and 8 fatty acids including lauric acid, palmitic acid and myristic acid were found in all samples. Palmitic acid had the highest average content (44.32%) among saturated fatty acids in the samples, followed by stearic acid (7.74%) and the unsaturated fatty acids with relative high contents of oleic acid (7.61%), linoleic acid (9.81%) and eicosanoid acid (12.16%). Ratio of unsaturated fatty acids in mangrove leaf samples fell within a range of 0.24-1.13. Unsaturated fatty acid had a lower proportion than that of saturated fatty acids in most samples, except in samples of X. granatum and B. gymnorrhiza (in Qinglangang). The proportion of unsaturated fatty acids in 4 species, i.e. R. stylosa, S. alba, C. tagal and L. racemose were higher in Tielugang samples than in Qinglangang samples, while the proportion in B. gymnorrhiza leaves was higher in Qinglangang samples. In terms of fatty acid composition, X. granatum and R. apiculate had higher similarity between the two sampling locations than those of other pairs of mangrove species. Difference in fatty acid composition among different leaf samples was mainly attributed to the variations of the contents of palmitic acid, linoleic acid and eicosanoid acid. Results suggested that the fatty acid composition of mangrove leaf samples was related to mangrove species and the sampling location, and the mangrove leaves in tropical areas might have generally low proportion of unsaturated fatty acids.