Abstract: Rare earth serves as an important strategic resource in China. It has wide applications in high-tech fields of permanent magnets, alloys, catalysts, petroleum refining, fine polishing, luminescent materials, glass ceramics and so on. Rare earth crystal is a kind of important high-end optical materials. Rare earth crystals refer to crystals in which rare earth elements can completely occupy a certain lattice in the crystallographic structure. As the key operation materials, rare earth crystals have been widely used in laser technology and ionizing radiation detection technology. Taking rare earth laser crystals, rare earth scintillating crystals, rare earth frequency doubling crystals and rare earth single crystal fibers as examples, the research progress in both composition design and performance optimization of high-end rare earth crystal materials in different applications were reviewed. For advanced growth techniques, the chemical bonding theory of single crystal growth would provide optimal growth parameters for multi-scale rare earth crystals, which could help us to obtain high-quality rare earth crystal materials.