The oxidative stability of f ish oil in different systems was studied by using peroxide value ( POV) , conjugated diene hydroperoxide content and fatty acids content as indexes. The results show that fish oil is most stable under the protect ion of N2 and most unstable when exposed in the air during storage. If f ish oil was dispersed in water to form an O/W emulsion system, its oxidative stability would be improved. In conclusion, if the oil system is secluded from O2, it might be one of the best ways to increase the oxidative stability of fish oil.