This paper presents the results of experiments which used Fe304 and Cu-doped Fe3O4 nanomaterials to remove As(III) from wastewater. The nanopartic1es were synthesized chemically and were observed by way of XRD, TEM and VSM measurements. The results show that the samples had a cubic crystalline phase structure, the grain size of about 8 - 12 nm and the values of magnetization Ms in range of 53 - 65.8 emu/g at room temperature. The magnetic saturation moment of the sample decreased as the Cu concentration increased. However, the adsorption data of the magnetic nanopartic1es show that the Cu-doped Fe3O4 nanoparticles could possibly have good arsenic adsorption when in a solution that has a pH from 5 to 11. In a solution with a pH 14, the arsenic adsorption of the magnetic particles was insignificant.