Highly oriented ZnO whiskers were prepared on glass substrates by metal-organic chemical vapor deposition (MOCVD) at atmospheric pressure. X-ray diffraction result reveals that ZnO whiskers grow along ［0001］ direction and the crystal structure of ZnO is of wurtzite type. Scanning electron microscopic observations show that the length and shape of the whiskers are almost uniform. The diameters range from 100 to 800nm ,and the curvature radius of the whisker tip is about 50nm or even less. The chemical reaction process during the preparation of whiskers is discussed and a simple growth model of ZnO whisker deposited by MOCVD is proposed.