The invention discloses a method for utilizing waste battery-grade iron phosphate, belonging to the technical field of waste treatment. The method comprises the following steps: drying and sieving waste battery-grade iron phosphate successively, then putting the waste battery-grade iron phosphate into a high-temperature furnace for high-temperature calcination, extracting exhaust gas generated bycalcination out and spraying the exhaust gas with pure water to obtain a phosphoric acid solution; subjecting iron oxide red to electromagnetic sorting to obtain an electromagnetically-sorted material, adding the sulfuric acid solution, and then carrying out filtering and washing to obtain a washed material; adding phosphoric acid and DAP into the phosphoric acid solution to obtain a mixed solution, mixing the mixed solution with the washed material, carrying out a reaction and then performing filtering to obtain a clear solution; adding urea into the clear solution, then carrying out heatingand a reaction, and then performing filtering and washing to obtain battery-grade iron phosphate and mother liquor; and subjecting the battery-grade iron phosphate to drying, sieving and electromagnetic iron removal, adding ammonia water into the mother liquor to adjust the pH value of a solution, and then carrying out concentration and crystallization to obtain DAP. The method provided by the invention can realize the resourceful utilization of the waste iron phosphate and cyclically prepares the battery-grade iron phosphate, and the added value of the product is high.