High methane conversion (1.1 mmol/h) and C2 selectivity (ca. 90%) were achieved simultaneously on Au60s/TiO2 for photocatalytic OCM. The enhanced activity was attributed to the introduction of Au co-catalyst, which played multi-functions roles: efficient hole acceptor, methane adsorption and activation site, and C–C coupling center. This work underscores the essential role of multifunctional co-catalysts, delving deeply into the structure-activity relationship through a synergistic combination of experimental and theoretical analysis. It is poised to serve as a significant milestone to inspire researchers in the field of photocatalytic OCM and beyond.