We report the synthesis of uniform-sized hexagonal ZnO nanocrystals by the thermolysis of Zn-oleate complex,which was prepared from the reaction of inexpensive and environmentally friendly reagents such as zinc nitrate and sodium oleate.Two organic compounds with different boiling points,octadecene and octylether,were selected as the medium for thermolysis of Zn-oleate complex.Under optimized reaction conditions,we were able to synthesize ZnO nanoparticles with the size being about 10 nm.X-ray diffraction and transmission electron micrograph(TEM) images confirmed the high crystallinity of the nanocrystals. We report the synthesis of uniform-sized hexagonal ZnO nanocrystals by the thermolysis of Zn-oleate complex, which was prepared from the reaction of inexpensive and environmentally friendly reagents such as zinc nitrate and sodium oleate. Two organic compounds with different boiling points, octadecene and octylether, were selected as the medium for thermolysis of Zn-oleate complex. Unit optimized reaction conditions, we were able to synthesize ZnO nanoparticles with the size being about 10 nm. X- ray diffraction and transmission electron micrograph (TEM) images confirmed the high crystallinity of the nanocrystals