Cu2O@Au yolk/shell structures were successfully prepared with a facile self-generated acid etching method at room temperature. The morphology is controllable by adding different amount of HAuCl4 center dot 4H(2)O. Scanning electron microscopy and transmission electron microscopy images showed that Au nanoparticles self-assembled into a porous shell around Cu2O core while the produced etching agent etched the core gradually and formed the cavity. The photocatalytic property of Cu2O@Au yolk/shell structures was studied by degrading MO under the irradiation of visible light at room temperature. Benefiting from the synergistic effect of cavity micro-reactor and electron transfer, the photocatalytic performance of the as-prepared Cu2O@Au yolk/shell structures was much better than that of pure Cu2O. The possible photocatalytic mechanism of the Cu2O@Au yolk/shell catalysts was proposed and elaborated in this study. It is certified that Yolk/shell structures have potential applications in photocatalysis for its active sites on the large specific area.