The invention discloses a method for preparing AlN powder. The method includes first dissolving an aluminum source and a nitrogen source completely in a solvent according to the Al:N molar ratio of 1:1-1:35, mixing evenly, drying the solvent by evaporating, roasting an obtained solid mixture at 500-1000 DEG C for 1-9h in a roasting atmosphere, and then decarburizing the mixture at 200-750 DEG C for 1 to 5h in an air atmosphere to obtain the high-purity AlN powder. The aluminum source is aluminum chloride hydrate, aluminum lactate, aluminum glycinate, aluminum stearate and the like; the nitrogen source is guanidine hydrochloride, guanidine acetate, chitosan, 1,10-phenanthroline; the solvent is any one of deionized water, methanol, ethanol, ethyl acetate, acetone, diethyl ether, benzene andtoluene; the roasting atmosphere is one or two of nitrogen, ammonia, argon and helium. Compared with the conventional AlN preparation method, the method has the advantages of wide reactant range, environmentally-friendly process, simple operation, high product purity and low cost.