The rare earth films with switchable optical properties were found recen tly.During the hydrogen absorption/desorption procedure or electrochemical charging /discharging,the optical properties of the r are earth hydrides can be changed dra stically.In this paper,the crystal structure and thermodynamic properties of rare earth hydrides were intr oduced,the progress in the switchab le optical properties of rare earth hydride films was briefly reviewed.The mechanism for rare earth hydrides with switchable optical propertie s was discussed as well.