The invention provides a compound sodium octaborate decafluoride, and a sodium octaborate decafluoride nonlinear optical crystal, a preparation method and application thereof, wherein the chemical formula of the compound is Na4B8O9F10, the molecular weight is 512.44, the compound is prepared by adopting a hydrothermal method or a vacuum packaging method, the compound belongs to an orthorhombic system, the space group is Pna2[1], the cell parameters are that a is 18.680(18)angstrom, b is 15.852 (16)angstrom, c is 4.816 (4) angstrom, alpha is 90 degrees, beta is 90 degrees, gamma is 90 degrees, the unit cell volume is 1425.9(7)angstrom<3>, the frequency doubling effect of the crystal is 0.7 * KH2PO4 (@1064 nm) and 0.1 * beta-BaB2O4 (@532 nm), the ultraviolet absorption edge is shorter than 200 nm, the crystal is grown through a melt method, a high-temperature melt method, a vacuum packaging method, a hydrothermal method or a room-temperature solution method, and the crystal is good in chemical stability and small in refractive index dispersion and can serve as a deep ultraviolet transmission nonlinear optical crystal to be applied to an all-solid-state laser.