Rare earth (RE) optical crystals are one kind of advanced optical materials, which are defined as the optical crystals therein RE elements occupy one lattice site of the crystallographic structure completely. They have been widely applied in the fields of military and national defense, national economy,science and technology. The research of RE optical crystals are based on the analyses of characteristics of rare earth ions and the phase diagrams, together with the application of chemical bonding theory of single crystal growth, thus the components, thecrystal growth methods and technique parameters of the crystalline materials are determined, and finally the bulk single crystals are obtained. The luminescence theory of RE ions, analyses of phase diagrams and components of several typical RE optical crystals are introduced briefly. The latest developments of several major kinds of RE optical crystals for the applications in various fields are reviewed. The research on rare earth optical crystals are important ways to achieve high-quality development ofrare earth resources, which require the collaboration of multidisciplinary courses and interdisciplinary fields.