Single crystals of K2B4O11H8, a non-centrosymmetric borate material, have been prepared by slow evaporation of water Solution at room temperature. The crystals were colorless and transparent with smooth faces. The single-crystal X-ray diffraction analysis showed that K2B4O11H8 crystallized in the orthorhombic space group P2(1)2(1)2(1) with a=6.8556(6)angstrom, b=11.7787(12)angstrom, c=12.8949(14)angstrom, Z=4, R-1=0.0188, and wR(2)=0.0464. The powder X-ray diffractometry (PXRD), infrared spectrum, transmittance spectrum, TG-DTA curves and second harmonic generation properties of title compound have been determined. (C) 2009 Elsevier B.V. All rights reserved.