The invention discloses a preparation method of magnetic/gold nano particles. The preparation method comprises the following steps: firstly adopting a co-precipitation method to prepare the magnetic Fe3O4 nano particles; polymerizing the dopamine in-situ on the surfaces of the magnetic particles to obtain Fe3O4 nano particles modified by the poly dopamine; introducing polyphenol and amino groups to the surfaces of the Fe3O4 nano particles; absorbing the nano gold seeds on the surfaces of the modified magnetic particles through the static action; adopting the nano gold which is absorbed on the surfaces of the magnetic particles as the seed, adopting the polyphenol on the surfaces of the magnetic particles as a reducing agent, gradually adding the chloroauric acid liquid to gradually produce the gold layers on the surfaces of the magnetic particles to obtain the core-shell magnetic/gold nano particles. The nano particles have good water dispersion and strong magnetic respond performance. The diameters of the nano particles are 30-100 nanometers, the saturation magnetization is 30.1-38.7emu/g, and the nano particles are superparamagnetic. The nano particles have wide application prospect on the fields of targeted drug controlled release, thermal therapy, separation of protein and enzyme, etc.