The surface plasmon resonance (SPR) effect of oxygen-deficient WO3–x has been utilized for photocatalysis in the literature. A unique feature of WO3–x is that its plasmonic peak can be adjusted to the visible light range, which is close to that of typical plasmonic metals like Au. In this work, we have demonstrated the coupling effect of the SPR of WO3–x and Au can significantly alter the photocatalytic activity toward the gas phase nonoxidative methane coupling reaction in terms of the C2 product rate and selectivity. A photocatalyst composed of Au and WO3–x nanoparticles of comparable size is prepared by the simple Pechini method and thermal reduction in a H2 containing atmosphere. The SPR of Au can mainly promote C2H6 production, while the SPR of WO3–x can mainly increase the selectivity to C2H4. Combining two such strategies can give a composite photocatalyst with a higher C2 production rate and almost 100% selectivity to C2H4 under visible light. Detailed characterization reveals that the coupling of Au and WO3–x can effectively prolong the charge lifetime and the charge generation rate, and improves the hydrogen evolution activity, which results in much higher photocatalytic activity.