The invention discloses a preparation method of rare-earth aluminoborate fluorescent powder and relates to red fluorescent powder. The invention provides a preparation method of the rare-earth aluminoborate fluorescent powder. A preparation technology is simple; the preparation method is easy to operate and environmentally friendly; the cost is low; and the fluorescent powder is easily excited by ultraviolet. The method comprises the steps of putting lithium carbonate, boric acid, aluminum oxide and europium oxide into an agate mortar for grinding at an element mole ratio of Li:Al:B:Eu of (2-x):1:1:x of a chemical formula Li2 x(AlBO4):xEu<3+>, obtaining a mixture, heating and roasting the obtained mixture in air, and grinding the mixture after cooling to form the rare-earth aluminoborate fluorescent powder, wherein x is greater than or equal to 0 and less than or equal to 0.25. The heating and roasting temperature of the rare-earth aluminoborate fluorescent powder is less than 1000 DEG C; the energy consumption is low; the mass production is facilitated; the fluorescent powder is stable in performance, can be excited by near ultraviolet rays, and emits 570-640nm fluorescent light; and a good spectral transformation material is provided for while LED (light-emitting diode) and crystalline silicon solar batteries.