Abstract:Inhibition of 17 different fatty acids on toxic Microcystis aeruginosa, Chlorella pyrenoidosa Chick and Scenedesmus obliquus Kütz were studied, and the structure-effect relationship was compared. All the 17 different fatty acids could inhibit the three algae but the strongest inhibition occurred on toxic Microcystis aeruginosa. The inhibitory effect of fatty acids correlated with their chemical structures, the more unsaturated linkages in fatty acid, the stronger the algal growth inhibited; the shorter the carbon chain of fatty acid, the better the algal growth inhibited. And the inhibition of fatty acids with odd carbon atoms on the algal growth was better than that of fatty acids with even carbon. The collective activity of multi-fatty acids showed synergistic growth inhibition on the three species of algae.