The hydro-generator is the core equipment in the hydropower system. Accurate temperature monitoring of the bearings of hydro-generator is crucial for condition assessment and ensuring the safe operation of the equipment. Compared to traditional methods, fiber Bragg grating (FBG) temperature measurement offers enhanced electromagnetic immunity and enables distributed temperature measurement. Therefore, this paper first introduces the basic principles, technical advantages and application of fiber Bragg grating temperature measurement technology. Then, combined with the actual needs of Unit 1 of an in-service hydropower station, a bearing temperature monitoring system based on fiber Bragg grating temperature sensors is designed. The operation principle, equipment selection and technical specifications of the key equipment of the system are briefly illustrated. Finally, the feasibility of fiber Bragg grating temperature measurement technology in the bearing temperature monitoring scenario of hydro-generator sets is verified based on the field test results. The fiber Bragg grating temperature measurement technology not only enhances the precision and reliability but also significantly improves the operation stability of the hydro-generator set. This study can provide theoretical support and technical reference for the application of fiber Bragg grating sensors in temperature monitoring of power equipment.