The invention relates to a compound barium fluoborate, and a barium fluoborate nonlinear optical crystal, a preparation method and application thereof, wherein the chemical formula of the compound isBaBOF3, the molecular weight of the compound is 221.15, the compound is prepared by adopting a solid-phase synthesis method or a vacuum packaging method, the chemical formula of the crystal is BaBOF3,the molecular weight of the crystal is 221.15, the crystal belongs to a monoclinic system, the space group is P2[1], the unit cell parameters are as follows: a is 4.6145(17)angstrom, b is 4.3671(16)angstrom, c is 7.905(3)angstrom and beta is 105.519(6)angstrom, the unit cell volume is 153.49(10)angstrom<3>, the powder frequency doubling effect of the crystal is about 1.0 time that of KH2PO4(KDP),the ultraviolet absorption edge is shorter than 190 nm, the crystal grows by adopting a melt method, a high-temperature melt method, a vacuum packaging method, a hydrothermal method or a room-temperature solution method, the chemical stability of the crystal is good, and the crystal can be used as an ultraviolet and deep ultraviolet nonlinear optical crystal to be applied to an all-solid-state laser device.