The structures of Agn clusters on CeO2(111),(110)and(100)surfaces,as well as on the partial reduced CeO2(111)are systematically investigated by density functional theory method.The theoretical results indicate that a single Ag prefers to adsorb at hollow sites on CeO2(111),(110)and(100)surfaces; the most stable Agn cluster on the stoichiometric CeO2(111)surface is generally with a 3D structure except Ag3 and Ag7.Agn(n=2-6)clusters on CeO2(110)and(100)tend to form a 2D structure.However,it aggregates again to form 3D structure with the increase of Ag atom number.