The synthesis of Manganese(III) oxide nanoparticles (Mn2O3NPs) was by visible light assisted approach using the TMA.OH, H2O2and metal precursor aqueous solution of MnCl2·4H2O. The formation of dark brown suspension was placed one day in the atmospheric air for the formation of the product via precipitation method during a process the product was accompanied by O2 gas generation. Dried aggregate was separated by filtration, washed with higherquantity of deionized water and methyl alcohol, and then dried at 80˚C for 16 h in air and finely were heated at 500 ˚C for 5 h. After the preparation Mn2O3NPs was tested using the following instrumental techniques such as UV-vis., FT-IR, XRD, FE-SEM. In this present investigation, Mn2O3NPs uses as photocatalyst over the degradation of Rhodamine B.