High-temperature sensors have important research and application value in aerospace, nuclear power, metallurgical industry, and other fields. To apply fiber Bragg gratings (FBG) to high-temperature sensing, this paper studies the preparation technology, annealing process, and temperature-wavelength fitting method of FBG arrays. First, a wavelength division multiplexed FBG array is prepared by the femtosecond laser point-by-point method, and FBG arrays with 9 different wavelengths in the range of 1510-1580 nm are prepared with optimized process parameters (femtosecond laser pulse energy, fiber moving speed, and FBG length). Then, the effect of annealing temperature and time on the center wavelength of FBG is examined, and the wavelength stability of FBG is improved by high-temperature and long-term annealing (700 ℃, 195 h), with the wavelength drift rate of FBG at 700 ℃ less than -2 pm/h. Finally, the high-temperature response of FBG with different center wavelengths are studied, and the general temperature-wavelength fitting functions of these FBG are obtained. The experimental results show that the temperature measurement accuracy of the FBG array sensor is better than ±1.8 ℃ at 700 ℃. The sensor is expected to be used for high-temperature measurement in extreme environments such as aeroengines, high-speed aircraft, and nuclear reactor cores.