[Zn(C7H3O5N)](n) (.) nH(2)O (1) possesses an anticlockwise windmill-like framework structure and formats spiroconjugation over the infinite molecular layer that is predicted to have large static third-order polarizability and the convergence value of gamma(xxxx) reaches 6.86 x 10(-33) esu in the case of zero input photon energy. The third-order NLO properties of 1 were investigated via Z-scan techniques at wavelength of 532 nm. It showed strong third-order NLO absorptive properties, and its n2 value was calculated to be 4.15 x 10(-11) esu. The relationship between the spiroconjugated structure and the NLO property has been discussed, which supposed to be more valuable for the NLO research. (c) 2006 Elsevier B.V. All rights reserved.