According to the requirement of quasi-distributed high temperature sensor based on fiber Bragg grating (FBG), preparation method of the FBGs with different periods is studied by using the femtosecond laser phase mask combined with fiber pulling. Periods of the FBGs are controlled by changing the stress applied to the fiber during femtosecond laser irradiation, then the quasi-distributed high temperature sensor based on the FBGs with different Bragg wavelengths is obtained. Temperature response parameter of the FBG is demonstrated, and two points quasi-distributed temperature measurement is achieved. The quasi-distributed sensor system is consist of the FBG demodulation instrument and FBGs with different Bragg wavelengths. Measured results of the FBG spectra under different temperatures indicate that the Bragg wavelength of the FBG is shifted linearly as the temperature increases. Reflectivity of the FBG keeps at -10.2 dB after annealing for a long time at 800 ℃. This FBG sensor system can be applicable to sensing measurement within 800 ℃.