The fatty acid composition and their changes at main developmental stages （ prophase-larvae, anaphase-larvae, juvenile and young） of the Pseudosciaena crocea were analyzed by means of GC/MS, and the comparison of fatty acids composition of the diseased juvenile with the normal juvenile was made. The fatty acids were detected, including 12 SFAs,6 MUFAs and 6 PUFAs. C14：0,C16： 0 （SFA） and C16：1,C18：1 （MUFA） were main source of energy metabolism during internal nutrition. The essential fatty acids C20：4（ n- 6）（AA） have existed in the larvae before its first feeding, while the DHA and EPA were only detected after feeding, and were affected by the bait kinds. The ranges of DHA and EPA content variety were 7.26% - 25.36% and 3.41% - 8.40% respectively. Compared with FA composition of the normal juvenile of the same period, the content of DHA and EPA in the juvenile with ＂swim bladder bnlge＂disease decreased clearly,with the DHA content being only 1/3 of the normal one, while the contents of AA,C18：1,C18：2,C18：3 and EPA/DHA specific value increased markedly,being 1.5- 3 times of those in normal juvenile. The inside reason that＂swim bladder bulge＂diseasc took place may be lack of DHA and EPA and higher AA.The research result can offer a theoretical foundation to prevent the ＂swim bladder bulge＂disease.