Utilizing thermal energy helium atom scattering we have made clear the dynamics from formation to destruction and the thermal stability of the Cs superstructures on a Pt(111) surface. Among three structures identified by low energy electron diffraction. both the (root3 x root3) and the (root3 X root3)R30 degrees structures are unstable and are destroyed at around 350 K, and transform into the (2 X 2) structure. The (2 X 2) structure which is stable up to 450 K, exhibits large corrugation amplitudes of the potential energy surface. This suggests a strong bond between Cs and Pt atoms and the localization of electron charge distribution as a result of the charge transfer from Cs atoms to the substrate Pt(111) surface. It is also suggested that the work function minimum is closely related to this charge transfer of Cs atoms forming the (2 X 2) structure.