Two novel noncentrosymmetric metal borates, Ba-2[B4O7(OH)(2)] (1) and Na[B5O7(OH)(2)](H2O) (2), have been obtained by hydrothermal and surfactant-thermal means. Compound 1 consists of novel one-dimensional borate chains formed by B3O9 and B3O8 rings, assembled into a three-dimensional (3D) framework by Ba2+ cations. The structure of 2 exhibits double-helical chains constructed from B5O10 primary building units, which are interconnected via Na+ cations and H-bonding interactions to generate a 3D framework. Second-harmonic-generation (SHG) measurements show that 1 shows a phase-matching powder SHG response of similar to 2.2 x KH2PO4 (KDP), while 2 exhibits a weak SHG response. The cutoff edges of 1 and 2 are similar to 242 and similar to 221 nm, respectively, which suggests that they are potential ultraviolet nonlinear optical (NLO) materials. Band structures and NLO properties have also been theoretically studied.