Mn and Cu-doped Cr2O3 nanoparticles were prepared by the co-precipitation method followed by calcination at 400 0 C for 3h. These synthesized nanoparticles were characterized by Fourier Transform Infrared spectroscopy (FTIR), X-ray Diffraction (XRD), Scanning electron microscope (SEM), Energy-dispersive X-ray spectroscopy, and UV/Visible spectroscopy. SEM images showed the irregular and nearly spherical structure of the Undoped and doped Cr2O3 nanoparticles respectively. The particle size of obtained nanoparticles exhibits in the range of 30-60 nm. X-ray diffraction study reveals at temperature 400 0 C, undoped and Cu-doped Cr2O3 nanoparticles exist in the crystalline phase and Mn-doped Cr2O3 nanoparticles exist in the amorphous phase. UV-Visible spectra have been used to determine the band gap of the synthesized nanoparticles. The optical band gap value has been calculated by using Tauc’s method and Kubelka Munk method. Results indicate band gap calculated by Kubelka-Munk method is higher (4.7, 4.5 and 4.32 eV) than Tauc’s method. (4.18, 4.0, 3.96 eV). It is also concluded the decrease in the band gap (in both Tauc’s and Kubelka Munk method) was observed by the addition of dopant.