Nonlinear optical crystal of CaN2B8O 26H32 has been grown with sizes up to 9 × 8 × 5 mm3 by the solvent evaporation method. The structure was determined by single-crystal X-ray diffraction and further characterized by powder X-ray diffraction and IR spectrum analysis. CaN2B8O 26H32 crystallizes in the orthorhombic system, space group P212121, with unit-cell parameters a = 11.556(7) , b = 12.583(8) , c = 16.679(8) , Z = 4, V = 2425.2(2) 3, R1 = 0.0263, and wR2 = 0.0655. The structure is made up of CaO7 polyhedra, and [B4O5(OH) 4]2- polyborate anions, NH4+ cations, and H2O molecules. UV-vis-NIR diffuse reflectance spectrum is performed on the CaN2B8O26H32, which shows an absorption edge <190 nm in the UV region. Thermal properties were investigated by TG analyses. The powder second-harmonic generation intensity measured by the Kurtz-Perry method indicates that CaN 2B8O26H32 has about half times that of KH2PO4.