The proximate composition and fatty acid profile of five tissues (head, skin, bones, muscle and liver) of juvenile Siganus guttatus fed with Enteromorpha prolifera were investigated. The results indicated that: (1) The content of protein and fat among these five tissues showed a significant differences (P Lass Than 0.05). The muscle has the highest content of protein and the lowest content of fat. (2) The highest content of fatty acid in SFA is 16:0 in all five tissues, the highest content of fatty acid in MUFA is18:1n-9c (cis) in skin, bones, muscle and liver, while the highest content of PUFA is DHA in muscle. Muscle contained the highest value of DHA and EPA, the total content was more than 100 times in bones. Muscle tissue is rich in many important polyunsaturated fatty acids such as EPA, DPA, DHA, ARA and ALA, which has better nutritional quality and immune and health function.