The invention discloses application of a multifunctional carbon quantum dot taken as a fluorescent whitening agent in the fields of spinning printing and dyeing, washing agents, papermaking, plastics, leathers or coatings and the like. The carbon quantum dot disclosed by the invention has the advantages of wide application field, good whitening effect and good light resistance, is innoxious and environmentally friendly, can be applied to the fields of spinning printing and dyeing, washing agents, papermaking, plastics, leathers or coatings and the like, and can generate unforeseeable technical effect because the carbon quantum dot can generate active oxygen free radicals under the condition of illumination, wherein the unforeseeable technical effect is as follows: the bacteria attached to the surfaces of spinning printing and dyeing materials, the washing agents, paper sheets, the plastics, the leathers or the coatings and the like can be effectively killed after the spinning printing and dyeing materials, the washing agents, paper sheets, the plastics, the leathers or the coatings and the like which are doped with the carbon quantum dot absorb ultraviolet light.