An apparatus for characterization of polycrystalline materials based on conductive atomic force microscopy(cAFM) is developed and a quantitative measurement of electrical characteristics of individual gains in polycrystalline ZnO ceramic is demonstrated. Improvement of the experimental method is presented. Experimental results illuminate unambiguously the different electrical characteristics between individual grains, suggesting the suitability and maneuverability of this method in the study of local structure or properties and their relationship in polycrystalline materials such as semi-conducting ceramics.