The fabrication and characterizations of nanocrystal-ZnO thin film used as active layer of MSM-photodetector structure are reported. The ZnO thin film were successfully sputtered on SiO2/Si substrates without heating or annealing processes by using a novel reactive gas-timing technique. In our experiment, the ZnO thin film properties with different gas-timing ratio of Ar/O2 were investigated. For fabricating of UV detector, the Al interdigitate electrode was deposited on SiO2/Si substrate by DC sputtering process and ZnO thin film was deposited as active layer. The response wavelength peak occurs at around 380 nm corresponding to ZnO energy bandgap of 3.2 eV .The I-V measurements indicates the Schottky behavior of ZnO on Al contact.