Abstract: Ethylene oxde is catalytically dissociated on silver surface. The first step of this reaction is to isomerize to acetyl aldehyde. The single collision catalytic di- ssociation probability is several orders of magnitude higher than the unimolecular reaction probability calculated by RRKM theory. Its activation energy decresese from 238 kJ mol~(-1) TO 42.6 kJ mol~(-1). The reaction order, reaction mechanism and product yield of this reaction are also described. These results will be helpful for the production of ethylene in industrial scale.