Modified magnetic microspheres were prepared and used to adsorb As ( ) from aqueous solution. The experiments were conducted in a batch system to study the adsorption behavior of As( ) onto these microspheres and the adsorption equilibrium, adsorption isotherm and kinetics were also studied. The experiment results showed that the modified magnetic microspheres are effective to remove As ( ) from aqueous solution, and the percentage removal of As ( ) could reach over 90% at pH 2.0 within 90 min. The pseudo second-order model was found to fit accurately with the experimental data. The adsorption isotherm can be described by Langmuir model.