Selective epoxidation of vinyl chloride on Ag(111),Pt(111)and Rh(I 11)with pre-adsorbed atomic oxygen has been studied by density functional theory(DFT)calculation with the periodic slab model.The reaction energies and activation energies of the epoxidation reaction are determined.Because of the asymmetry of vinyl chloride,three competitive reaction pathways are investigated.The results indicate that the most possible reaction pathway is pathway Ⅲ.Compared the activation energies of the epoxidation reaction on Ag(111),Pt(111)and Rh(111),it is obvious that the reaction via OMMC(3)on Ag(111)is the most possible process.However,the selectivity to the target product over Ag(111)is the lowest among the three metals.The results also indicate that the formation of chloroacetaldehyde is more favorable than that of chloroepoxide.