Clean　and　O-(2　2　×　2　)　R45°　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.　©　2024　Chinese　Physical　Society.