ZnO transparent thin-film transistors with MgO gate dielectric were fabricated by in-situ metal organic chemical vapor deposition(MOCVD)technology.We used an uninterrupted growth method to simplify the fabrication steps and to avoid the unexpectable contaminating during epitaxy process.MgO layer is helpful to reduce the gate leakage current,as well as to achieve high transparency in visible light band,due to the wide band gap(7.7eV)and high dielectric constant(9.8).The XRD measurement indicates that the ZnO layer has high crystal quality.The field effect mobility and the on/off current ratio of the device is 2.69cm2V-1s-1 and～1 × 104,respectively.