In view of the particularity of the structure of the secondary mirror base in the space environment, it is necessary to monitor its temperature state, thus a FBG temperature sensor with metal base is designed for the application of satellite secondary mirror seat. By changing the distance of fixed points, combining the principle of optical fiber temperature sensing with the strain state of bent gate region, a substrate with small structure and light weight is designed, and also it can realize multiposition temperature measurement simultaneously. Experimental results show that the linearity of the temperature sensor reaches 0.999 in three bands, and the sensitivity is 10.78, 10.81 and 10.36pm/℃ respectively for the three bands. The center wavelength of the sensor fluctuates within ±3pm at the same temperature, which is less affected by external stress and has good repeatability.