Ripplon light scattering technique is introduced together with its application to the study on physical properties of molecular films formed on liquid surfaces. Ripplon is high frequency capillary waves generated by the thermal fluctuation of the liquid displacement, of which propagation constants yields information on the molecular dynamics in and near the surface. The ripplon frequency and damping constant is determined accurately by the light scattering system equipped by the optical beating spectroscopy techniques. The technique was successfully applied to the investigation of two dimensional gas-liquid phase transition of the Langmuir films. It reveals the critical behavior of the film, which is observed as the critical softening of the condensed phase with increasing temperature. Several other applications of ripplon light scattering for the observation of dynamic process of molecular adsorption/desorption process on to the surface are also presented.