Identification of molecular-level mechanisms of methane activation is very important in order to transform the most stable alkane molecule into value-added chemicals. Herein, by employing a homemade time-of-flight mass spectrometer coupled with a vacuum ultraviolet (VUV) laser system, the reactions of neutral heteronuclear metal oxide clusters AuxAlyOz (x = 1, 2) with CH4 have been investigated. The interesting channel of Au2Al2O3H+ production was observed for the interaction of a Au2Al2O3 cluster with CH4 after VUV ionization, suggesting that the methyl radical was generated. Combined with the theoretical calculations, this study proposes that VUV ionization of the neutral adsorption complex (Au2Al2O3CH4) creates an active cation (Au2Al2O3CH4+)* to induce C–H bond activation and the methyl radical formation. The photochemistry of this cluster study provides molecular-level insights into the interactions between methane and active sites in related photocatalytic processes.