Abstract: Conventional transformer oil level is monitored by electric signal sensor,and the sensor signals are susceptible to interference from transformer high voltage,high current and other complex electromagnetic environment.For the above shortcomings,a transformer oil level gauge based on fiber Bragg grating sensors was proposed.That was fiber bragg grating oil level gauge,which was mainly composed of a fiber bragg grating sensor and a C-type spring tube.And the oil level for transformer conservators was monitored by the strain characteristic of the fiber bragg grating and the relationship between the liquid pressure and the height of the liquid level.It was a non-electricity monitoring method to improve the stable operation of transformers.The experimental results showed that the center wavelength deviation of the fiber bragg grating oil level gauge was linear with the change of the oil level for the conservator,the average linearity fitting was 0.9996 and the average sensitivity was 4.7472 pm/dm,which was filled the monitoring requirements of the oil level in conservator.