The present invention relates to a preparation method for GaN nano powder doped with Mg, Mn or Cu. The preparation method comprises the following steps of: firstly preparing mixed solution of analytically pure Mg, Mn or Cu and gallium nitrate Ga(NO3)3 with different mole ratio quantity, wherein the concentration of Ga<3+> 0.01mol/L to 0.02mol/L, then adding the analytically pure absolute alcohol with the capacity of being 6 to 7 times of the quantity of an aqueous solution, adjusting pH between 6 to 7.5, carrying out ultrasonic oscillation and obtaining a precursor with an amorphous structure. The precursor is different from the precursor prepared by the wet method, and the GaN nano powder doped with different elements can be obtained after ammoniation according to difference of the doped elements; and the doped GaN nano powder can be used as packaging materials. The method has simple equipment, simple and convenient operation, does not need expensive devices, and can obtain GaN and doped GaN nano powder with low cost and high efficiency.