A magnetically recoverable adsorbent has been prepared by silica-coated magnetic nanoparticles through an amine functionality (ASMNPs). The ASMNPs were characterized by XRD, TEM, SEM, and FT-IR spectroscopy. It was used as an efficient and economical adsorbent for removing O, O-Diethyl O-[4-methyl-6-(propan-2-yl) pyrimidin-2-yl] phosphorothioate (diazinon) from contaminated water through batch experiments. The results were shown that 84% of diazinon was removed after 30 min. The experimental data of the adsorption kinetics were well described by Pseudo-second-order kinetic model (R2>0.99), and Equilibrium adsorption data could be better fitted with the Freundlich isotherm (R2>0.99). The standard free energy change (ΔG°) and standard enthalpy change (ΔH°) were indicated that this system is a spontaneous and exothermic process.