Abstract: A modified mesoporous silica (MCM-41) is prepared by chemical modification. Amino functionalized mesoporous silica (NH2-MCM-41) was prepared by co-condensation method, employing hexadecyltrimethylammonium bromide (CTAB) as template, tetraethoxysilane (TEOS) as the silicon source, and 3-aminopropyl triethoxysilane (APTES) as modifying agent. Chlorpyrifos was choosed as the model pesticide, and the chlorpyrifos/amino functionalized mesoporous silica system were prepared using the impregnation method. The structures, morphologies, Zeta potential and loading of chlorpyrifos of MCM-41 and NH2-MCM-41 were systematically studied using X-ray diffraction assay (XRD), N2adsorption-desorption, transmission electron microscopy (TEM), scanning electron microscopy (SEM), Zeta potential and fourier transform infrared spectroscopy (FTIR). The adsorption capacity (AC) and slow-release performmance of chlorpyrifos were also discussed. Besides, the interaction between NH2- MCM-41 and chlorpyrifos is investigated. The results showed that MCM-41 and NH2-MCM-41 have ordered mesoporous structure of the hexagonal phase. The AC of MCM-41 is 106 mg/g, while the maximum AC of NH2-MCM-41 is 178 mg/g. And the AC increases with the increase of the Zeta potential of NH2-MCM-41. The APTES was beneficial to improve the slow-release performance of MCM-41 of chlorpyrifos. The corresponding releasing curves could be described by Higuchi equation.