The invention discloses a preparation method for a positive material-lithium iron phosphate of a lithium-ion battery. The preparation method adopts a preparation process of uniformizing a solution, drying and calcining. The preparation method comprises the following steps: uniformly dispersing iron salt, lithium salt and phosphate into the solution by adding a proper complexing agent without precipitate generating, selectively adding proper soluble doped metal salt and a carbon-source precursor to obtain a mixed solution, drying the mixed solution, calcining under the inert atmosphere, and preparing the positive material-lithium iron phosphate of the lithium-ion battery. The preparation method disclosed by the invention has the advantages that the mixed solution is adopted as the reaction precursor, the raw materials do not need to be ball-milled, the process is simple, the energy consumption is low, the operability is strong, the large-scale production is easily realized; and the lithium iron phosphate material is uniform in composition, controllable in components and fine in crystal grain, and can be used as a high-quality positive material of the lithium-ion battery.