The lipid content and composition of the reef-building coral Acropora downingi, the largest coral reef of Hengam Island, were examined throughout a year. The results showed that the lipid content of A. downingi significantly differs in different seasons (t-test, P< 0.05). Depending on the season and spawning times, the lipid content of A. downingi ranged from 16.5 to 37.7 % (dry weight). The total lipid content was the lowest in the cooler and the highest in the warmest seasons, when solar irradiance were at their highest. Gas chromatography-mass spectrometry (GC-MS) analysis of fatty acid composition of the lipid contents showed that palmitic acid (16:0) was the most abundant fatty acid component of these lipid classes, and other fatty acid concentrations were as follows: Stearidonic acid (18:3, n-6), Eicosapentaenoic acid (20:5, n-3) and Stearic acid (18:0), respectively.