Preparation method of iron phosphate

The invention discloses a preparation method of iron phosphate, which comprises the following steps: pretreating wastewater in the production process of iron phosphate, adsorbing and concentrating the pretreated filtrate through phosphorus removal resin to obtain a regenerated liquid, and concentrating the regenerated liquid through nanofiltration salt separation to obtain a concentrated liquid; and mixing the concentrated solution with a phosphorus salt solution in iron phosphate production to prepare a phosphorus salt mixed solution for iron phosphate production to obtain iron phosphate. According to the method, pure water is recycled through chemical precipitation, filtration and reverse osmosis in combination with MVR, then phosphorus salt is concentrated through a method of phosphorus removal resin adsorption regeneration and NF membrane salt separation process separation, the concentration of the phosphorus salt is high, impurities are few, a phosphorus source with relatively short resources is recycled