In this study, a high-temperature sensing array based on a femtosecond fiber grating was designed to address the temperature measurement needs of high-power spallation targets. The temperature range and mechanical strength of the sensor were enhanced using a femtosecond laser-engraved fiber grating and a tubular encapsulation method. The annealing process, i.e., annealing steps, annealing time, and annealing temperature, was investigated and optimized. Additionally, multiple annealing (800 ℃, 20 h) was conducted to improve the stability of the fiber Bragg grating. An accurate fitting function of temperature-wavelength was obtained through its calibration test. The sensor has an accuracy of ±0.2 ℃ in the temperature range of 100-500 ℃, with good repeatability. Moreover, on-site testing results indicate that the proposed sensor can achieve precise temperature testing of high-power spallation targets.