Abstract: High-quality ZnO films were grown on GaN/Al₂ O₃ substrate by using atmospheric-pressure metal-organic chemical vapour deposition.H 2 O and Zn（C₂ H₅）₂ were used as the O and Zn sources,and nitrogen was used as the carrier gas,respectively.The ZnO films were stu died in detail via high resolu-tion double-crystal X-ray diffraction.The Full-width athalf-maximum（FWHM） of the （0002）ω-rocking curve is 404arcsec,indicating that the ZnO films arestrongly c-oriented. The FWHM of the （0004）ω-2θrocking curve is 358arcsec,whichin dicates that the ZnO films aresingle crystals.The samples show threading dislocation densities of order of 10⁸/cm², by the asymmetric FWHM of （1012）ω-rocking curve.Moreover,the （1012）peaks of ZnO and GaN were simultaneou sly obtained by ω-2θ scan,which further confirms the high quality of the ZnO samples.