The invention discloses a method for reversely extracting and co-production of industrial-grade phosphate by using phosphate mother liquor for wet-method purification phosphoric acid, which is capable of lowering the production cost. The method comprises the following steps of a, adding a defluorination agent, an adsorbent and oxidizing agent in wet-method purification phosphoric acid for defluorination and decolorization; b, extracting phosphoric acid with an extraction agent, adding inorganic acid in the middle of an extraction tower; c, desulfurating and washing; d, reversely extracting with industrial-grade phosphate mother liquor; e, finely tuning slurry; f, feeding the finely tuned phosphate slurry into a crystallizer for crystallizing, then carrying out solid-liquid separation and drying to obtain product industrial-grade phosphate, wherein the slurry obtained from solid-liquid separation is industrial-grade phosphate mother liquor which is subjected to pH value adjustment and returned to step d for use. Reverse extraction is carried out by cooled and crystallized industrial-grade phosphate mother liquor, the reverse extraction effect is good, the step of evaporation is avoided, desulphurization and washing are carried out simultaneously, the procedures are simplified, and the production cost is saved. A new preparation method of the industrial-grade phosphate is provided.