α-phase bismuth oxide nanoparticles successfully prepared by precipitation method and characterized with thermo gravimetric analysis and differential thermal analysis, X-ray diffraction, Photo luminance, Field emission scanning electron microscope, Energy dispersive X-ray diffraction FT-IR spectra and UV-Vis diffuse reflectance spectroscopy. The bismuth oxide particles annealed at 500 °C exhibited α-phase. Photocatalytic experiments indicated that the obtained Bi₂O₃ nanoparticles were highly active for photodegratation of methline blue.