In order to accurately demodulate temperature information from the sapphire crystal temperature sensor,a demodulation system based on discrete gap transform(DGT) is established.Based on the principle of white light polarimetric differential interferometry,the demodulation method of the single crystal sapphire high-temperature sensor illuminated by Gauss distributed optic source is demonstrated via DGT.In order to improve the non-uniform sampling digital light frequency error existing in traditional Fourier transform demodulation,the feasibility of measuring optic path difference (OPD) is presented by directly applying a DGT algorithm to the data sampled at equal optical wavelength interval and using the relation between OPD caused by temperature and the peak amplitude of DGT.The demodulation precision is improved by suppressing the background spectrum noise with the Gauss window.With the help of the demodulating system,the experimental results show that the method can be used for precise high temperature measurement within 600-1 200 ℃.