Due to some limitations of traditional methods about oil temperature and level monitoring in transformer conservators, an intelligent monitoring system based on fiber Bragg grating sensors to monitor the change of oil temperature and level in transformer is proposed in this paper. This system is composed of five parts: fiber Bragg grating sensors, sensor data processing and storage, intelligent evaluation of the characteristic information of the transformer, cooperation of the monitoring and evaluation results. The oil level sensor is composed of a fiber Bragg grating sensor and a C-type spring tube, and the oil level can be monitored by the relationship between pressure and height of the liquid pressure. This method can improve the stable operation reliability of the transformer without electricity detection. The experimental results show that the central wavelength of the fiber Bragg grating sensor changes linearly with the oil temperature and level in the transformer. The intelligent monitoring system can be achieved in high voltage, electromagnetic interference and other complex environments without electricity detection, which can greatly improve the safety and reliability of the transformer.