Abstract: Effect of additives on light stability of insulating oils with different aromatic contents was studied. The results show that light stability of high-pressure hydrorefining oil containing no aromatics is better than that of solvent refined oil with certain aromatics. The degree of impact of hindered phenolic antioxidants on light stability of insulating oils varies with different antioxidants. The more the antioxidant added in insulting oil, the sooner the color changes. Only when the antioxidant runs out, does the color of insulating oil return to that of oil with no antioxidants. The more the antioxidant content, the longer it takes to recover to normal. Adding some metal deactivator to insulating oil will produce sediment.