To solve this problem, this paper proposes an on-line temperature measurement system based on fiber Bragg grating (FBG) which can obtain the actual temperature of winding during transformer operation. provide real-time and accurate temperature measurements, overcoming the limitations of traditional methods such as RTDs (Resis ance Temperature Detectors) and thermocouples, have limitations in terms of accuracy, sensitivity, and susceptibilit r Bragg Grating (FBG). FBGs are periodic variations in. monitoring system for transformer winding temperature solves this problem perfectly. The temperature-dependent change of the refractive indices of the fiber, consequently the shift of its Bragg wavelength, is used as a measure of the temperature.