The invention discloses a preparation method for GaN nanoparticles. In the method, the mixture of gallium nitrate and melamine is sequentially roasted in high temperature under an inert atmosphere and an air atmosphere, and thereby the GaN nanoparticles are obtained. The purity of the GaN nanoparticles prepared by the method disclosed by the invention is high, the preparation process is simple and easy to operate, the cost is low, and the invention has the prospect of industrialized application.