As a temperature sensor, fiber Fabry-Perot (F-P) cavity sensor is widely used. Improving the photoelectric properties of the materials and components of the optical fiber is conducive to improving the sensitivity of the temperature sensor.A F-P temperature sensor based on SiGe core fiber is prepared based on fiber fusion and polishing technology. The preparation process comprises the following steps: firstly, splicing the general single-mode fiber with the SiGe core fiber by using optimized splicing parameters, and then polishing the SiGe core fiber by means of optical fiber polishing, the length of which can be precisely controlled by observing the free spectrum range of the reflection spectrum during the polishing process. The experimental results show that the spliced end face is smooth and flat, and the intensity of the reflection spectrum is 7.7 dB higher than that of the single-mode fiber. The SiGe core optical fiber F-P cavity sensor has a high temperature sensitivity, which can reach 116.1 pm/℃.