The interaction of CH4 with a Pt(111)-(2x2)-O surface has been investigated by a supersonic molecular beam scattering technique. CH4 irradiation is found to completely remove oxygen atoms from the surface via CH4 oxidation reaction, CH4+O-->CO+H-2. The reaction is found to be translationally activated. The oxidation probability of CH4 on Pt(111)-(2x2)-O is found roughly an order of magnitude greater than the initial dissociative chemisorption probability of CH4 on Pt(111), especially under a low incident kinetic energy condition. From the angular intensity distribution and the time-of-flight distribution measurements of scattered CH4, no significant difference in the collision dynamics of CH4 both on Pt(111) and on Pt(111)-(2x2)-O is recognized. (C) 2003 American Institute of Physics.