Three isomers of nitrophenol molecules were loaded in one-dimensional channels of AlPO4-5 by vapor-phase diffusion process. The resulting materials (o-NP/,m-NP/ and p-NP/AlPO4-5) have been characterized by thermoanalytic and spectroscopic methods, and their nonlinear optical properties have been investigated in powder form. From the results, these materials were found to exhibit second harmonic generation (SHG). The order of SHG intensity was m-NP/AlPO4-5 < p-NP/AlPO4-5 < o-NP/AlPO4-5, and SHG intensity of o-NP/AlPO4-5 remarkably depended on amount of loadings.