Diffusion of arsenic atoms affects the quality of interface magnetic integrated device and the physical properties of the structure. A method was put forward to improve the interface magnetism by passivation process. The valence band spectrum and core level spectrum were measured by synchrotron radiation photoemission. Experimental results confirm interface diffusion of As atoms. The result was compared with that from Fe/GaAs without passivation and it is confirmed that passivation has attenuated diffusion of arsenic atoms; Fe 3d band is expanded by exchange-splitting interaction, showing the Fe film in good magnetic order and the magnetism of Fe film has been enhanced. According to the large exchange splitting in valence band spectra and the related results, it can be concluded that passivation technology can be used to improve the quality of integrated magnetic devices.