Combining plasmonic noble metals with semiconductor materials has been considered to be an effective way to improve catalyst performance. In the present paper, Au nanoparticles (NPs) were decorated onto CVD-grown -Ga2O3 nanowires (NWs) through a chemical reduction method. Different quantity of HAuCl4 solution was used to control the size and density of Au NPs. The photocatalytic activity of the Au-Ga2O3 NWs is evaluated by degrading rhodamine B (Rh B) under UV and visible light irradiation. It is found that the size and density of the Au NPs had a great influence on the photocatalytic efficiency of -Ga2O3 NWs. And Ga2O3 NWs with Au NPs of 5.7nm size and 420/m(2) density shows the best catalytic efficiency. Moreover, Au NPs attachment on the Ga2O3 could extend its photocatalytic activity towards the visible light irradiation, which is significant to efficient utilization more solar light. A jointly effect of both the interfacial Schottky potential field between Au NPs and -Ga2O3 NWs and local surface plasma resonance excitation is proposed to contribute the enhancement effects.