In this paper, ZnO thin film was first grown on the sapphire fiber-ending by electron-beam evaporation, which has good morphology and high crystallization quality. The transmittance spectra showed that the sharp optical absorption edge has a red shift with increasing temperature, and the obtained temperature-dependent band gap energy for ZnO follows to the linear relation Eg（T）=340-491×１０-4T. This formula presents the key to fabricate new broad\|measurement range fiber-optic temperature sensors based on semiconductor ZnO by utilizing the optical absorption spectra at different temperatures.