Abstract: Deep-ultraviolet nonlinear optical crystal, a class of functional materials, is the core material in hotolithography, micro-machining and high resolution photoelectric spectrometer．These crystals are classified here by their structural building unit into two categories: those with a π-conjugated system (including borates, carbonates and nitrates) and those with a non-π-conjugated system (such as phosphates, sulfates, and silicates)．Their crystallographic structure, major optical properties (including linear and nonlinear optical properties), and strategies of their syntheses are summarized．This brief review should shed some useful light on future explorations of novel deep ultraviolet nonlinear optical crystals．