As the key devices of the deep-ultraviolet(DUV,wavelength below 200 nm)all-solid-state lasers,DUV nonlinear optical(NLO)crystals have attracted increasing attention in the near decades.KBe2BO3F2(KBBF)is the unique crystal that can directly generate the sixth harmonic laser of Nd: YAG lasers(wavelength = 177.3 nm).Though the optical performances of KBBF crystal are excellent,its intrinsic drawbacks like toxicity and layered growth habit limit the commercial applications.Thus,the design and synthesis of new DUV NLO crystal is of urgent demand.1 Our group have proposed a design strategy for DUV NLO materials by introducing the BO3F,BO2F2,and BOF3 new fundamental building units(FBUs)into borates.2 Under this material design strategy,a series of fluorooxoborates with excellent optical properties have been synthesized,such as Li2B6O9F2,2 AB4O6F(A = NH4,Na,Rb,Cs,K/Cs,Rb/Cs)series,3-6 and MB5O7F3(M = Ca,Sr).7 It was demonstrated that all these materials have short absorption edges,large NLO responses,and suitable birefringence to satisfy the DUV phase-matching.From the insight of structure-properties relationship,their superior properties are largely attributed to the diverse B-O/F anionic groups and improved anisotropic polarizabilities.The experimental and calculated results strongly suggest that these new compounds are outstanding DUV NLO materials.