In order to further optimize and improve the fixed mode of optical fiber sensor, an extrinsic Fabry-Perot(F-P) optical fiber sensor with metal solder chip is designed and experimentally observed. The failure mechanism of F-P optical fiber sensor with different welding fixed mode at 1200 ℃ high temperature is studied and analyzed. The experimental samples that failed under 1200 ℃ high temperature are observed and analyzed. The finite element analysis method is used to simulate and calculate the experimental samples and the actual spectral signal changes are combined to study the specific failure process. The result show that different welding fixed mode will have different mechanical effects on the sensor, which will affect the life of the sensor.