The invention belongs to the field of new chemical materials and in particular relates to a carbon quantum dot/attapulgite nanocomposite as well as a preparation method and application thereof. The preparation method comprises the following steps: mixing citric acid, hydrogen peroxide and attapulgite, carrying out hydrothermal reaction, and then centrifuging, washing and drying, so that the carbon quantum dot/attapulgite nanocomposite is obtained, and then the nanocomposite is used for photocatalytic desulphurization.