Nano-ZnO powder was prepared by using Zn(NO3)2 and (NH4)2CO3 as starting materials. The aggregation of nano-ZnO powder particles was studied by the Zeta potential system, infrared absorption spectra, XRD and SEM. The results showed that a suitable dispersant added to the ZnO precursor could increase the static potential of nano-ZnO powder, which would restrain aggregation of the precursor during the drying and calcining process. In this way, the dispersed state of the ZnO nano-powder is improved. The particle size of prepared ZnO powder is less than 20 nm. Secondary particle size is less than 80 nm.