Abstract: Disclosed are a thermosetting light-reflective resin composition, a method for preparing the same, an optical semiconductor element-mounted reflector produced therefrom, and an optical semiconductor device including the same. More specifically, disclosed are a thermosetting light-reflective resin composition which includes a polyhydric polyol having two or more hydroxyl groups and thus exhibits superior discoloration resistance and entails little deterioration in reflectance, a method for preparing the same, an optical semiconductor element-mounted reflector produced therefrom and an optical semiconductor device including the same.