The invention relates to a preparation method and application of a lithium borate birefringent crystal. According to the crystal, the chemical formula is Li3BO3; the molecular weight is 79.63; the crystal belongs to a monoclinic system; the space group is P21/c; the cell parameters are that a is equal to 3.2637 (8) angstroms; b is equal to 9.180 (2) angstroms; c is equal to 8.319 (2); beta is equal to 101.039 (2) degrees; V is equal to 244.63 (11) angstroms 3; and Z is equal to 4. The crystal is used for infrared-deep ultraviolet bands, is an aniaxial negative crystal, and has a transmission region of 175 to 3,500nm; double refraction ranges from 0.080 (4,500nm) to 0.140 (175nm); and a high-temperature solution method is adopted to grow the crystal. The crystal obtained by the method described in the invention is easy to grow, cut, grind, polish and preserve, stable in air and difficult to airslake, can be used for manufacturing polarized beam splitter prisms such as Glan prisms, Wollaston prisms, Rochon prisms or beam splitting polarizers, and thus has important uses in the fields of optics and communication.