Abstract: Clean and O-(2\sqrt 2 ×\sqrt 2 ) R45^o Cu(100) surfaces were prepared to study the impact of surface oxygen on the activation of methane dissociation. Auger electron spectroscopy, low energy electron diffraction, infrared reflection absorption spectroscopy, scanning tunneling microscope, and a quadrupole mass-spectrometer for temperature programmed desorption were used to explore the behavior of CH₄ on the two surfaces. The dissociative adsorption of CH₄ was observed on oxygen-pre-covered Cu(100) but not on the clean surface indicating surface oxygen promotes the dissociation of the C–H bond. This study can be a reference for the conversion of methane into other high-value-added products with high efficiency and low energy consumption.