Deep ultraviolet nonlinear optical crystals are the core materials of all-solid-state deep ultraviolet laser sources, which can change the laser frequency through nonlinear optical effects and output deep ultraviolet lasers with wavelengths shorter than 200 nm. They have important application values in deep ultraviolet laser lithography, semiconductor chip defect detection, high-end scientific research equipment and other fields. In recent years, a series of progress has been made in the research of new deep ultraviolet nonlinear optical crystal materials, and candidate materials with excellent comprehensive performance have emerged. This paper focuses on the crystal materials with experimentally measured refractive index and phase-matching wavelength reaching the deep ultraviolet region, summarizes the research progress in material discovery, crystal preparation, basic properties, and structure-property relationship, and discusses the development trend of practical deep ultraviolet nonlinear optical crystal materials.