Nano-sized silver catalysts have been prepared by alcohol and dioctyl ester of sodium sulphosuccinic acid, anionic surfactant, Aerosol OT(AOT). TPD/TPR and ethylene oxide activity have been studied to investigate the characteristics of silver catalysts. The sizes of Ag particles were estimated to be 10 ~ 16 nm and the peak of silver oxide was not observed by XRD except for metallic silver. The desorption peak of molecular oxygen by TPD/TPR uniqely observed at about 400 ℃ in the catalyst prepared by water-alcohol method. However, in the catalyst prepared by microemulsion method, the desorption peaks of molecular and atomic oxygens were observed at about 400 ℃ and 600 ℃, respectively. The catalyst prepared by water-alcohol method showed higher activity ethylene oxide than the catalyst prepared by microemulsion method. It seems due to the larger silver particles and easier desorption of molecular oxygen from the catalyst prepared by water-alcohol method.