A number of zinc oxide (ZnO) films are deposited on silicon substrates using the magnetron sputtering method. After undergoing thermal treatment under different conditions, those films exhibit hexagonal wurtzite structures and different photoluminescent characteristics. Besides the notable ultraviolet emission, which is related to the free exciton effect, a distinct blue fluorescence around 475 nm is found in some special samples. The blue photoluminescence emission of the ZnO film is believed to be caused by oxygen vacancies.