Au/Fe,3,O,4, composites were formed by irradiating the aqueous solution of HAuCl,4, containing poly(vinyl alcohol) (PVA) with UV light at a wavelength ,λ,=254 nm in the presence of Fe,3,O,4, nanoparticles. The properties of the as-prepared composites were characterized by means of ultraviolet spectra (UV-vis), X-ray diffraction (XRD), and transmission electron microscopy (TEM), respectively. XRD pattern confirmed the face-centered cubic phase of Au nanoparticles in the composites. The surface plasmon resonance band of the sample was rather narrow, which indicated a relatively narrow size distribution of Au nanoparticles. TEM revealed that Au/Fe,3,O,4, composites with a size range of 70~230 nm had cluster structure, composed of a number of Au and Fe,3,O,4, nanoparticles. Furthermore, it turned out that PVA was necessary for constructing the composites. A possible mechanism was proposed for the formation of Au/Fe,3,O,4, composites.