Abstract: Direct electrical measurement of single grain boundary of ZnO piezoelectric ceramics with micron fine grains is carried out based on the nanomanipulator installed in the scanning electron microscopy(SEM). With two probes clamped on the manipulator as microelectrodes, the volt ampere characteristic curve, nonlinear coefficient of ZnO piezoelectric ceramics grain boundary and the average size of twenty grains are measured. The experimental data are represented by impedance complex plane through equivalent circuit fitting in the frequency range from 20 Hz to 1 MHz. The result shows that the essence of low-frequency direct circuit high resistance impedance can be attributed to grain boundary and the electrical resistances distribution at 20 Hz can be used to predict the impedance characteristics of ZnO piezoelectric ceramics at some lower frequencies.