A method of fabricating optical fiber microcavity based on hydrofluoric acid etching technology is proposed and designed. An all-fiber (Fabry-Perot, F-P) multi-beam interference filter structure is formed by welding a 4. 5mm long single-mode optical fiber. The main interference spectrum period is 20.7nm and the secondary interference spectrum period is 1. 4nm; on this basis, the fiber F-P filter as the frequency selection device constitute an erbium-doped fiber laser system, and narrow linewidth laser output with center wavelength of 1560.40nm, signal to noise ratio of 15. 441dB and 3dB linewidth of 0. 28nm is realized. In the experiment, the optical fiber F-P filter was heated and cooled by the temperature heating platform in the experimental temperature range of 360~430C. The laser wavelength was red-shifted during the heating process, and the temperature sensitivity of the sensing system was 13. 80pm/C, the linear fitting degree is 99. 82%; the temperature sensitivity of the laser sensing system during the cooling process is 13. 36pm/C, and the linear fitting degree is 99. 44%.The experimental results provide a laser system measurement method for high-precision high-temperature sensing.