Abstract: The integrated technology of sensing optical fiber and transformer electromagnetic wire is expected to solve the problem of distributed testing of transformer winding temperature. An embedded electromagnetic wire structure was proposed, which realized the stable combination of the sensing optical fiber and the electromagnetic wire. The experiment showed that the maximum optical loss of the sensing optical fiber winding in different methods with this structure was 3.116dB. The measured and theoretical micro-strain error under different curvature radii was about 6%, which made it clear that the curvature radius of the coil should not be less than 25mm. What mentioned above verified the feasibility of the integrated technology of sensing optical fiber and transformer electromagnetic wire. On this basis, a 10kV transformer was developed and tested. The results show that the embedding of the sensing optical fiber has no effect on the insulation characteristics of the transformer. The average temperature and hot spot temperature errors of the low-voltage winding measured by the sensor optical fiber are +0.8℃ and +2.7℃ respectively, which verifies the accuracy of the temperature measurement. Furthermore, the simulation and measured results of temperature rise are compared, which helps to improve the calculation accuracy of temperature rise. The research conclusions provide a new idea for the realization of the sensing and monitoring of the temperature state of the transformer winding.