A method for synthesizing lithium iron phosphate as a material for the cathode of lithium batteries is disclosed. This method comprises mixing and sintering the lithium source, iron source, phosphorous source, and carbon source, wherein said iron source is a mixture of FeC2O4 and FeCO3, with a molar ratio of FeC2O4 to FeCO3 of 1:0.5-4. The purity and specific capacity of lithium iron phosphate produced using are both relatively high, and the method of this invention is very safe in practice.