The invention discloses an acid dye. The acid dye is prepared from resorcinol, bromamine acid, poly-naphthaldehyde sodium sulfonate, sodium silicate, dodecyl diphenyl ether di-sodium sulfonate, pyrazolone, deionized water, a defoamer and an additive. The acid dye is efficient, environmentally friendly, high in stability, convenient to use and high in adhesive force. By optimizing dye constituents and using the self-made additive in a matched mode, tinting strength is improved, the problem that the chinlon acid dyed fabric fixation effect is poor when a traditional acid dye is adopted is solved, and wet fastness is improved extremely. During preparation of the acid dye, constituents are divided into two parts to be mixed and treated respectively and then mixed finally, and by means of the added additive, the constituents of the dye can be homogenized extremely and the dyeing effect and dyeing quality of the dye are improved.