Without using SP enhancement technique, the surface second harmonic generation (SHG) from Ag film was obtained by employing the 1.06μm output from a Q-switched YAG laser. The changes in the SH signal due to adsorption of pyridine molecules on the Ag film were investigated. It is confirmed for the first time that pyridine could be adsorbed on Ag film surface even at atmospheric pressure and room-temperature.