The effect of lysine or methionine addition on the lipid oxidation and protein properties in casein-fish oil model system during the storage of 21 days at 37$^{circ}C$ was studied. The peroxide and TBA values were increased markedly and the amino acids addition to the system caused to reduce the extent of lipid oxidation in comparison with that of casein-fish oil system which was a control group. Significant changes in fatty acid composition of each group were observed. Polyenoic acid contents were drastically decreased during the storage in the groups with and without the amino acids additions, . And also significant losses of several amino acids were occurred with the reduction of solubility and digestibility of casein during the storage. However no different effects were observed in both additionsof lysine and methionine to the system.