By means of FFAP capillar y gas chromatograph column in this pape r studied fat ty acids compost ion in gonad total lipid of St rongylocent rotus intermedius , St rongylocentrotus nudus and G lyp tocidar is crenularis , lipid contents were determinated at the same time .Results showed that ther e are more than forty kinds fat ty acid in those species of sea urchin , and their dist ributions were very similar .The main HUFA were 18∶4n -3(3 .2 %～ 7 .4 %), 20∶4n -6(6 .4 %～ 16 .7 %)and 20∶5n -3(6 .6 % ～ 12 .1 %), general polyenoic acid content was 50 % or so .In addit ion , very seldom n -5 and n -7 olefinic acids were discover ed , for instance , n -5 ser ies enoic acid , 18∶1n -5 , 20∶1n -5 , 20∶2n -5 , 11 and 20∶2n -5 , 13 , total content was 7 .6 %～ 10 .2 %, n -7 ser ies enoic acid wer e 22∶2n -7 , 13 and 22∶2n - 7 , 15 , the ir contents were r ather low(0 .7 %～ 1 .2 %).