Afacile solution-phase route for the synthesis of shape-controlled ZnO nanocrystals in a polyol/water mixture system was developed. The obtained nanocrystals were characterized by X-ray diffraction, transmission electron microscopy and UV-visible absorption spectroscopy. The results indicate that modulating the adding ways of water has a significant effect on the shape of the obtained nanocrystals. The addition of small quantity of water can increase the growth rate of crystals and leads to the formation of different shapes. The resulting shapes of the novel structures are diverse,including spheres, cones, and teardrops, all of which are obtained without any additional surfactants.These studies concerning the shape evolution of nanocrystals should be valuable for further design and for greater understanding of advanced nanoscale building-block architectures.