The invention relates to a complete cycle preparation method of lithium iron phosphate by using lithium ores as a lithium source, comprising the following steps: carrying out calcining, acidifying, leaching, purifying and separating on the lithium ores to obtain a primary lithium liquid, carrying out conversion and refrigeration, filtering and washing, evaporative concentration on the primary lithium liquid to obtain a lithium liquid for synthesis, letting the lithium liquid for synthesis, a ferrite solution, and a phosphor source solution be subject to liquid phase synthesis, and calcining to obtain the carbon coated lithium iron phosphate. According to the invention, cooling crystallization, separation, drying and other steps in the preparation of lithium iron phosphate with lithium ores are left out, and the byproducts obtained by evaporative concentration, filtering and separating are recycled, so that the utilization rate of resource is increased, and the cost is saved; and the prepared lithium iron phosphate has the characteristics of high purity, excellent electrochemical performance and the like, so that the circular economy is realized.