Polyunsaturated fatty acids (PUFAs) are a special kind of bioactive substances with important biological functions. PUFAs are the magnitude membrane component of nerve and other cell membranes. Eicosanoid produced from arachidonic acid and eicosapentaenoic acid can regulate inflammatory responses and the functions of T and B lymphocytes. PUFAs play important roles in the growth, development, immunity and survival of fish by affecting the lipid metabolism, gene expression, membrane functions, immunity and biochemical characters of the blood. The present paper reviewed the influence and mechanism of PUFAs on fish immunology, as well as the regulation of PUFAs on the survival of larvae, which would benefit the field study, improve the use of PUFAs, promote immunity and the survival of fish.［Chinese Journal of Animal Nutrition, 2010，22（3）:551-556］