This study on the effect of 12L: 12D cycle and continuous light intensity (8000 lx, 4000 lx, 2000 lx 12h: 12h L D cycle and 4000 lx) on the total lipid content and fatty acid composition of three species of marine microalgae (Chlorella sp-2, Isochrysis galbana, and Amphidinium sp.) showed that the major fatty acids of Chlorella sp-2 were 16: 0, 16:1 (n-7) and 20:5 (n-3); those of Isochrysis galbana were 14:0, 16:0, 16:1(n-7), 18:4(n-3), and 22:6(n-3); and those of Amphidinium sp. Were 16:0, 18:1(n-9),18:4(n-3), 20:5 (n-3) and 22:6 (n-3). The total lipid contents of Chlorella sp-2 and Isochrysis galbana grown at higher light intensity were higher than those grown at lower light intensity. Generally, their percentage of the saturated and monounsaturated fatty acids increased with light intensity. The total polyunsaturated fatty acids decreased with increasing light intensity. EPA content decreased with increasing light intensity and the was no obvious changes in DHA as light intensity increased.