ZnO thin films with the c-axis orientation on the (0001) sapphire substrate were grown by metal-organic chemical vapour deposition. It was demonstrated that the Ⅵ/Ⅱ precursor flow-rate ratio can influence strongly on the structure and opto-electrical properties. With the increasing Ⅵ/Ⅱ ratio of 130:1, the full width at half maximum of (0002) peak in x-ray diffraction is only 0.184℃, the near-band-edge emission enhances remarkably and the intensity ratio of the near-band-edge emission to the deep-level emission reaches 237:1 in the photoluminescence spectrum. At the same time, the resistivity and mobility increases to 3.28 × 102Ω.cm and 25.3 cm2 V- 1 s- 1. These facts indicates that the quality of the ZnO thin films could be improved by increasing the Ⅵ/Ⅱ flow rate ratio during the growth.