A kind of photoemissive thin films, which does not contain alkali elements but contains metallic ultrafine particles, is studied. A typical kind is the thin film of silver ultrafine particles embedded in the barium oxide. There are two methods in the formation of Ag-O-Ba thin films: single-metallic layer method and multimetallic layer method. The photoelectric emission response curve to wavelengths between 350 and 800 nm is given. The energy band with respect to the position diagram in the neighborhood of its surface is also presented. This kind of photoemissive thin films can be exposed or stored in the atmosphere and can be used again in a vacuum system without reactivation process for laser-pulse detection.