ZnO nanosheets with the wurtzite structure have been successfully synthesized via a microwave-assisted solution method. The thicknesses of ZnO nanosheets are in the range of 5-10 nm and lateral sizes up to 1 mu m. The surfaces of ZnO nanosheets are +/- (1210) planes of wurtzite structure. The as-prepared products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM). The optical and thermal properties were investigated with UV-Visible absorption spectra, thermogravimetric analysis (TG) and differential scanning calorimetric analysis (DSC).