ZnO microstructures have been grown from zinc chloride (ZnCl2) and ammonia solution at 100 degrees C for 1??24 hours. X-ray diffraction, scanning electron microscope and field-emission scanning microscope were utilized to investigate the structural properties and morphology of the ZnO crystals. Structural investigations show that phase-pure hexagonal structure ZnO has been successfully synthesized, and the hexagonal structure ZnO can be achieved in solutions with an appropriate range of concentrations. Under our experimental conditions, several different morphologies of ZnO structures were obtained, including flower-like and bar flower-like. The relationship between the morphology and experimental conditions are discussed.