The invention relates to an optical fiber Bragg grating temperature sensor for measuring temperature of a dry type air-core reactor and an application method of the optical fiber Bragg grating temperature sensor, and belongs to the technical field of photoelectron measurement. The tail part of an optical fiber Bragg grating is connected with an optical fiber; the lead-out optical fiber penetrates out from a polytetrafluoroethylene sleeve and is adhered and fixed by epoxy resin, so as to play a role in protecting the optical fiber; a rectangular gap is formed in the middle of the left end of a polytetrafluoroethylene plate; a transverse round hole is drilled in the gap, and is used for planting the optical fiber Bragg grating; the optical fiber Bragg grating is in a cantilever beam structure in the round hole, fills the rectangular gap by a polytetrafluoroethylene material after being planted, and is integrally encapsulated into a rectangular structure together with the polytetrafluoroethylene plate; the temperature change of the dry type air-core reactor is calculated according to the relational expression delta lambdaB is equal to KT multiplied by deltaT of a displacement value of a center wavelength of the optical fiber Bragg grating and the outer encapsulation temperature of a lead of the reactor. The optical fiber Bragg grating temperature sensor is suitable for temperature detection in a strong electromagnetic field environment, and is high in anti-corrosion capability and very small in size.