The invention relates to the field of textile materials, and particularly discloses a nano negative ion fiber material, a preparation method thereof and application of the nano negative ion fiber material in a cosmetic brush. The nano negative ion fiber material is prepared from 50-70 parts of epoxy resin, 20-30 parts of graphene oxide, 10-15 parts of nano silver, 10-15 parts of nano zinc oxide, 1-10 parts of opal, 10-15 parts of quartz powder, 2-15 parts of acrylic acid, 0.5-2 parts of benzoyl peroxide, 5-15 parts of an additive, 5-10 parts of an antibacterial agent and 2-5 parts of a dispersing agent. The preparation method comprises the following steps that the epoxy resin, the graphene oxide, the acrylic acid, the benzoyl peroxide and the dispersing agent are uniformly mixed to obtain a mixture, water is added into the nano-silver, the nano-zinc oxide, the opal, the quartz powder, the additive and the antibacterial agent to obtain a mixed solution, the mixture is mixed with the mixed solution, drying and melting are carried out to obtain the nano negative ion fiber material. The nanometer negative ion fiber material can be used for preparing bristles of the cosmetic brush and has the advantages of being soft, high in powder grabbing force, capable of whitening skin and the like.