This paper reports a synthesis of zinc oxide (ZnO) nanosheets by hydrothermal method. ZnO nanosheets on Al substrate were generated by hydrothermal synthesis with zinc nitrate hexahydrate (Zn(NO3)2$6H2O) and hexamethylenetetramine (HMT) as a research system, which were controlled conditions of the reaction. The energy dispersive spectroscopy (EDS), scanning electron microscope (SEM) and transmission electron microscopy (TEM) images were achieved to determine the characterization of ZnO nanosheets. The diameter of ZnO nanofilm was from 0.5 to 1 μm, and its thickness ranged from 30 to 50 nm.