The invention relates to nano-crystal fluorescent powder and a preparation method thereof. The invention belongs to the technical field of luminescent materials. The nano-crystal fluorescent powder is Cu-In-Znx-E/ZnS, wherein E=S or Se, and x is no smaller than 0. The preparation method comprises steps that: copper salt, indium salt, alkanethiol and octadecene are isolated from oxygen, mixed, andheated; long-chain alkyl organic acid is added to the product, the mixture is isolated from oxygen and is heated, such that a reaction source is obtained; zinc salt, long-chain alkyl organic amine and octadecene are isolated from oxygen, mixed, and heated, such that a zinc source is obtained; when E=S, the zinc source is added to the reaction source, and the mixture is heated, such that a colloidal solution 1 is obtained; when E=Se, selenium powder is dissolved, and an obtained selenium source is added to the reaction source; the mixture is heated, such that a colloidal solution 2 is obtained; the zinc source is added to the colloidal solution 2, and the mixture is heated, such that a colloidal solution 3 is obtained; the colloidal solution 1 or 3 is washed, and is subject to vacuum drying, such that the nano-crystal fluorescent powder is obtained. According to the invention, the nano-crystal fluorescent powder contains no rare earth element; the luminescence wavelength is adjustable;the nano-crystal fluorescent powder can be uniformly dispersed in an organic solvent; and the application range of the nano-crystal fluorescent powder is wide. The preparation method is advantaged inhigh yield, low cost, environment-friendliness, easy operation, and suitability for large-scaled productions.