Abstract In our experiment, the major aim is to study the changes in green emission intensity of ZnO powder after various ratio of carbon black added. The effects of process parameters, such as heat treatment temperature, the type of solvent and precipitants, the ratio of carbon black, on the particle morphology and sizes are investigated. The sizes of the prepared ZnO are estimated by XRD and TEM techniques, and the morphology is observed by SEM analysis. We calculate also the concentration of oxygen defects and Zn interstitials by EPR analysis. In PL test, we can find the green emission intensity is the largest when the weight ratio of carbon black to ZnO powder is 0.3:1, the ZnO powder produced with oxalic acid dihydrate as precipitant especially.