[en] Magnetite (Fe3O4) nanoparticle were prepared by hydrothermal process in two ways, which would be used for production of copier toner.In this investigation, the first process was made from ferrous sulphate (FeSO4 . 7H2O) by using 10 M sodium hydroxide solution. In this method, magnetite nanoparticles were prepared by changing aeration time from 1 to 3 hr and heated at 90C for 15 min. The alternative process was carried out from ferrous sulphate (FeSO4.7H2O) by using 6.6 M sodium hydroxide solution and sodium silicate solution.Magnetite (black iron oxide) was synthesized by using different aeration times and reaction times. Aeration time was changed from 1 to 2 hr and reaction time was changed from 1 to 5.5 hr at 85 C. The magnetites obtained were examined by X-ray Diffraction (XRD) analysis and Scanning Electron Microscopy (SEM) technique. The average particle size range of magnetite nanoprticles were 90-120 nm and 120-150 nm in each process. The maximum yied percentages of magnetite based on FeSO4 in both processing were found to be 46.30% and 60.72%. The precent yields of magnetite in both preparation based on theoretical yields were 91.02% and 94.83% respectively.