Effects of additives on physical properties of dower sole skin gelatin prepared by fractional precipitation with ethanol were investigated to obtain basic data for utilizing as food protein source. Physical properties such as gel strength, melting point, gelling point and viscosity of both ethanol- and non-treated gelatins were improved as ferric ion, sugar and ethanol were added to gelatin sol, but were deteriorated as sodium hydroxide and acids were added. Insignificant difference in effects of physical properties on additives such as ferric ion, sodium chloride, sugar, acids and ethanol between ethanol- and non-treated gelatins were not observed.