Abstract: With pressure monitoring of the transformer oil tank, we can grasp the pressure change process caused by gas production when serious internal defects occur, and take timely measures to ensure the safe operation of the transformer. Existing pressure sensors are generally metal-encapsulated or with air chamber structure, which poses a threat to the insulation of transformers if used directly inside. To this end, this paper proposed a new insulation-friendly optical pressure sensing method with temperature compensation. The fiber grating was encapsulated with fluorosilicone rubber inside and supplemented by an epoxy resin shielding shell on the outside. At the same time, the proposed structure adopted the double grating cross arrangement, which further improved the pressure measurement sensitivity, and the pressure sensitivity reached 15pm/kPa while avoiding the interference of the temperature rise. The results prove that the sensing structure is suitable for all kinds of oil-immersed power equipment, and can operate normally in a discharge environment, completely record the oil pressure changes caused by the breakdown of the oil gap, and sensitively sense small pressure changes in early failures.