18 Red Acid Dyes is one of the azo eyes that are currently used in the textile industry. Photocatalytic degradation offers great potential as an advanced oxidation process. 18 Red Acid Dyes are the photocatalytic degradation of Acid red 18 that is made by using BiOI/ZnO nanocomposite and was evaluated under visible light irradiation. It is a water solution and strong hydrochloric red acid, add sodium hydroxide that is brown. It is mainly used for wool, silk, polyamide fibre and its blended fabric dyeing, and also can be used for leather, paper, plastic, wood, medicine and cosmetics of dyeing, still can make the ink.