Ten cultivated strains of Pyropia yezoensis were studied in this research in order to identify the effects of the strain difference and the harvesting time difference on the fatty acid composition and content of P.yezoensis. The results showed that the fatty acid composition of these ten P.yezonsis samples was not affected;however,the content of each fatty acid was affected and the difference among ten samples was significant.The saturated fatty acids (SFAs)were mainly composed of 13∶0,16∶0,18∶0 with 16∶0 as the highest component(about 20%).The unsaturated fatty acids(UFAs)included 18∶1 n-9,18∶2 n-6,18∶3 n-3,20∶1 n-9,20∶2 n-7,20∶3 n-7,20∶4 n-6(AA),20∶5 n-3(EPA)and the major componet was EPA(about 50%).Samples harvested during the lowest water temperature period(February)contained the highest total fatty acids and EPA concentration;the result indicates that the low water temperature has advantages in accumulating fatty acids especially UFAs of P.yezoenis.P.yezoensis is rich in UFAs(especially EPA).The n-6/n-3 ratios ranged from 4.9 to 7.7 during the whole study period,and this range is consistent with the recommended diet ratio of WHO/FAO.