The invention discloses a preparation method for iron phosphate nanosheets. The preparation method comprises the steps that iron black is slowly added to phosphoric acid with the concentration of 1.5-3.0 mol / L, stirring and heating are conducted for reacting, and after the reaction, the iron phosphate nanosheets are obtained through suction filtration, washing, drying, dewatering and other steps.The iron phosphate prepared by using the method has a nanosheet-shaped morphology, the thickness of the nanosheets is 70-80 nanometers, and the specific surface area is high. By optimizing the reaction conditions, in the reaction procsess, the pH value does not need to be adjusted, and no oxidizing agents are added; the interference with anionic and cationic impurities is effectively avoided, theiron phosphate obtained by using the method is free of impurity phases and high in purity. Besides, less water is used for washing iron phosphate precipitation, the iron phosphate synthesizing cost isreduced, and the pollution to the environment is reduced. The technology is simple, operation is convenient, industrial production is facilitated, and the preparation method is wide in application prospect.