Abstract: Provided area deep ultraviolet non-linear optical crystal of barium borate hydrate, a preparation method therefor and the use thereof. The chemical formula of the crystal is Ba2BHO22H7, belonging to monoclinic system, with the space group thereof being P21, the crystal cell parameters thereof being a=6.7719(10) ?, b=21.1195(4) ?, c=6.8274(10) ?, ?=119.3950(10)° , and the molecular weight thereof being 752.65. The non-linear optical crystal of borate is obtained by means of programmed cooling or natural cooling using a hydrothermal method. The crystal powder has a frequency-doubled effect of about 2 times that of KDP (KH2PO4) and an ultraviolet cut-off edge of below 175 nm and can be used as a deep ultraviolet non-linear optical crystal. The growth process of the crystal has advantages such as simple, a low cost, a low toxicity, a short growth cycle, stable physical and chemical properties, etc.