The invention relates to an ecological antioxidant for improving the photooxidation resistance of a natural dye dyed fiber product. The antioxidant comprises superoxide dismutase, and also comprises one or more of trehalose, deoxidize enzyme, lipoic acid and chlorogenic acid, the antioxidant concretely includes superoxide dismutase, chlorogenic acid and lipoic acid according to a mass ratio of (1-5):(1-5):(1-5). The antioxidant is mainly used for post-treating the natural dye dyed fiber product to make the fabric related fastness improved. The antioxidant has the advantages of high efficiency,environmental protection, greenness, non-toxicity, good durability and the like, a treatment method has the advantages of low cost, simplicity, convenience, good operability and the like, and the antioxidant and the treatment method lay a foundation for the improvement of the wearability of the natural dye dyed fiber product, and solve the problem of oxidative fading of a natural dye.