The invention relates to a preparation method for gold nano-particles. The preparation method comprises the following steps: first, preparing a nano-gold material which is provided with a shell substrate by taking mussel shell powder as a carrier and combining a liquid phase reduction method and an ultraviolet radiation catalytic method without adding a protective agent; removing shells to obtain relatively pure gold nano-particles. The method provided by the invention is simple in required equipment, convenient to operate, short in preparation period, non-toxic, environment-friendly and low in cost, and can be applied to industrial batch production; the prepared gold nano-particles are pure and have controllable particle sizes. Therefore, the preparation method can serve as a new direction for developing an environment-friendly gold nano-particle preparation method.