The UV-vis spectrophototometer was applied to investigate the aging process of red carminic acid, under alkali, acid, UV light, heat, oxidizing atmosphere and reducing atmosphere treatment. The results have shown that carminic acid is tolerable to acid and UV light. It is sensitive to alkali and heat. Poor stability is shown in oxidizing and reducing atmosphere. UV-vis spectrophotometry is a simple and rapid way for the study of dye aging.