Chlorine fastness improver, and preparation method and application thereof

The invention discloses a chlorine fastness improver, and a preparation method and an application thereof. The chlorine fastness improver comprises, by mass, 1-5% of polyacrylate, 5-48% of a hydrazide derivative, 0.5-6% of a dispersant, and the balance of water. The hydrazide derivative concretely is one or more of octanedioic dihydrazide, azelaic dihydrazide, sebacic dihydrazide, dodecanedioic dihydrazide, isonicotinoylhydrazine, 1,2-diisonicotinic acid hydrazide, 1,2-dimethyl-1,2-dibenzoylhydrazine and isophthalic dihydrazide. The preparation method of the chlorine fastness improver is simple, and the chlorine fastness improver makes chinlon and spandex swimming suit dyed fabrics have the advantages of effectively improved chlorine fastness, small color change, good handle, good chlorine fastness and good water wash resistance.