Abstract: Twostep method was developed for separation and purification of EPA and DHA from fish oils.EPA and DHA were first enriched by aqueous AgNO₃ complex.As the concentration of aqueous AgNO₃ was more than 4M at 293.2K,most of EPA and DHA were selectively transferred into aqueous phase from oil phase.Then,the preconcentrated EPA and DHA were further refined by rectifying technology of supercritical CO_２. The effects of pressure ,temperature gradient of the rectification column,flow rate ,quantity and composition of feed were examined.The optimum conditions were given.90.3%EPA and 91.4%DHA were obtained with the yield of about 40%at the same time.