Nanoparticles of bismuth oxide were successfully synthesized by hydrothermal process which included Bismuth (III) nitrate (Bi(NO3)3.6H2O), sodium hydroxide(NaOH) and Nitric acid(HNO3) without further purification along with ultra-pure water. To investigate the structural, optical, and photocatalytic activity of two samples (1:5) and (1:6) respectively with two different NaOH precipitating agent molar ratios. The prepared nanoparticles were characterized by X-ray diffraction (XRD), UV-Vis’s spectrometer, scanning electron microscope (SEM), Energy-dispersive X-ray spectroscopy (EDAX), Fourier transform infrared spectroscopy (FTIR) and X-ray Photo electron Spectroscopy (XPS). Based on the obtained results the hydrothermally synthesized Bi2O3 NPs exhibit good efficiency to photocatalytic degradation of Methylene blue under the irradiation of LED white light.