Single crystal of Li(H2O)(4)B(OH)(4)center dot 2H(2)O has been synthesized via hydrothermal method and its structure was determined by single crystal X-ray diffraction. The space group of Li(H2O)(4)B(OH)(4)center dot 2H(2)O is P3 with cell parameters a = b = 6.5601(4)angstrom, c= 6.1748(3)angstrom, and Z=1. The crystal lattice structure is composed of four B(OH)(4) tetrahedra, one Li(H2O)(4) tetrahedron and two isolated water molecules. Powder X-ray diffraction (XRD), infrared (IR) spectroscopy, UV-vis-IR diffuse reflectance spectroscopy, powder second harmonic generation (SHG) measurements and TG/DSC analysis were performed for the title compound. It reveals that the SHG efficiencies of Li(H2O)(4)B(OH)(4)center dot 2H(2)O is about 0.8 times that of KH2PO4 (KDP). The direction and magnitude of the dipole moments in BO4 and LiO4 units of Li(H2O)(4)B(OH)(4)center dot 2H(2)O have been quantified using the bond-valence approach, which shows that the SHG response originates from the cooperation of BO4 and LiO4 units along c axis. (C) 2016 Elsevier Ltd. All rights reserved.