With the development of industry, high temperature sensing is widely used in the industrial field, which not only requires high precision, good stability and fast response of high temperature sensors, but also hopes to reduce the manufacturing cost of sensors. Optic fiber high temperature sensor can well meet the above application requirements, and has a good development prospect. At present, the common fiber optic high temperature sensor structure too pursues the improvement of sensitivity at the expense of stability. At the same time, the processing process is complex and difficult to batch preparation.A femtosecond laser micromachining system was employed to precisely ablate the air microcavity located at the end of a single-mode fiber, thereby creating a fiber FPI structure. Three distinct structures of varying dimensions were fabricated, and the reflection spectra of these samples were analyzed using Fourier transform techniques. The temperature sensing characteristics of the samples within the range of 200-800 ℃ were evaluated. Finally, the high temperature stability of the sensor at 800 ℃ was measured, and the detection accuracy was calculated. The three samples were processed by femtosecond laser, and the air microcavities were all 30 μm, and the distance between them was 20, 40, 80 μm, respectively. The maximum error of sample processing size was not more than 1 μm. The preparation process had good repeatability, the insertion loss was around 11 dB, and the fringe contrast of the samples was greater than 10 dB. The temperature sensing characteristics of the sensor at 200-800 ℃ were measured. The temperature sensitivity at 200-400 ℃ was 8.6 pm/℃, and the high temperature sensitivity at 400-800 ℃ was 11.3 pm/℃. Finally, in the stability test experiment, the maximum deviation of the measured temperature did not exceed ±1.77 ℃, indicating that the structure had good stability.A high-temperature optic fiber sensor based on Fabry-Perot interferometer was designed and fabricated by using femtosecond laser microfabrication. The sensor has high accuracy, good stability, compact probe structure, small size, flexibility, and strong adaptability. It has potential application value in high-temperature measurement environments with long distances and narrow spaces. Three different sizes of samples were prepared in the experiment, verifying the feasibility of the processing technology and providing certain reference value for industrial low-cost and mass production.