A preparation method for lithium iron phosphate, a positive electrode active material, a positive electrode plate, a battery, and a power-consuming device. The preparation method for lithium iron phosphate includes: dissolving a first iron source, a second iron source, a lithium source, and a phosphorus source in a solvent to obtain a mixed slurry; and subjecting the mixed slurry to sintering treatment to obtain lithium iron phosphate. The first iron source includes at least one of iron oxide or first iron phosphate. The second iron source includes at least one of second iron phosphate or ferrous oxalate. An iron-to-phosphorus ratio of the first iron phosphate is 0.97 to 0.985. An iron-to-phosphorus ratio of the second iron phosphate is 0.93 to 0.96. Primary particles of the lithium iron phosphate, which have different particle sizes, can be blended.