The surface potential of Zn1-xMgxO/ZnO heterostructure grown by radical source molecular beam epitaxy was measured by Kelvin force microscopy (KFM). A clear correlation was observed between the topographic image and the surface potential of Zn0.56Mg0.44O/ZnO heterostructure. The potential area around the surface pits was about 60 mV lower than that of the surrounding region, which suggests the effects of the pits on the electrical properties of the potential layer. In order to guarantee the accuracy of measurement, the probe shape was analyzed by probe characterizer and using Au thin films as a potential standard. (C) 2009 Elsevier B. V. All rights reserved.