Abstract: In the upper atmosphere 100 ~ 300 km above sea level, the atomic oxygen, one of the main constituents, is chemically active and can be easily adsorbed and even corrode surfaces of vehicles flying in very low earth orbits. This phenomenon will significantly change the physical and chemical properties of surfaces as well as the gas-surface interactions characteristics, and then affect the aerodynamic performance of vehicles. Due to the cost limitations and huge distinction in space-time scales, it is difficult for current ground tests and simulation methods to duplicate the gas-surface interaction processes in the real space environment of the upper atmosphere. To solve this hard problem, an equivalent method of molecular dynamics simulation is designed in this study, which allows gas molecules to impinge on the surface at a high frequency in a short time to capture the main features of long-time but low-frequency gas-surface interaction processes in the real environment. Thus, the evolution of oxygen atoms' adsorption/corrosion state on the surface of a typical aero-space material is explored, and the momentum accommodation processes at different altitudes are analyzed. The results indicate that when certain equivalence principles are satisfied, this simulation method can reasonably reveal the real physical pictures, showing three evolution stages of the surface state, i.e., (1) adsorbing a few oxygen atoms, (2) adsorbing a large number of oxygen atoms, and (3) corroded by oxygen atoms and covered by a loose oxide. At the same time, the momentum accommodation characteristics of high-speed incident gas molecules on the corresponding surface states are also investigated. Moreover, the existence of another main component N₂ in the upper atmosphere is also considered and its effects on the adsorption, corrosion and accommodation of oxygen atoms are evaluated. This study can deepen the understanding of gas-surface interactions in the upper atmosphere and provide instruction for the aerodynamic design of the upper atmosphere vehicles.