Cobalt (II, III) oxide is an inorganic compound with the formula Co3O4. It is a blackantiferromagnetic solid. As a mixed valence compound, its formula is sometimes written asCoIICo2 III O4 and sometimes as CoO.Co2O3. The XRD result confirmed the formation of simplecubic crystal structure of the Co3O4. The average crystallite size of the samples are found toincrease with increase in annealing temperature. The optical energy band gap values estimatedby UV-visible analysisreported that the energy band gap values are increased with increase incalcination temperature. So that Co3O4 nanoparticles are used as p-type semiconductor. ThePhotoluminescence sharp peaks shows a near and edge emission located at UV region and greenemissions.