Abstract: The brittle fracture of composite insulators is a malignant fracture accident.Therefore, we investigated the brittle fracture monitoring of composite insulators. Four optical fibers were pasted on the surface of the fiber-reinforced plastic (FRP) rod of a 10 kV composite insulator, one of which has 2 fiber Bragg gratings (FBGs) to measure temperatures, and the others have 5 FBGs to measure stresses. Temperature calibration tests, tension calibration tests, and stress corrosion tests were carried out on the rod with surface-encapsulated FBGs. The results showed that three cracks appeared in the stress corrosion tests of the rod, of which crack 1 developed into a brittle fracture, and the other two did not. The temperatures and the stresses in the entire brittle fracture process of the rod were monitored by the FBGs on the rod surface. It is found that the stress corrosion process can be divided into four stages as follows: no change in the initial stage, corrosive heat release in the second stage, crack initiation in the third stage, and finally, the cracks developing rapidly until the rod break. From the second stage, the heat begins to emit in the corrosion zone, and the maximum difference between the corrosion zone temperature and the ambient temperature reaches 2.46?, thus a temperature difference of 1? can be used as an early warning for the second stage in the brittle fractures of composite rods. The stress FBGs can detect a crack with an axial distance of 20 mm between them, and a wavelength shift 1.1?_wmax or 0.9?_wmin of the stress FBGs can be used as an early warning for a crack initiation or a serious crack in the brittle fracture process of composite insulators, respectively. By the FBGs monitoring method in this paper, a technical means can be provided to investigate fracture mechanisms and materials against brittle fracture/decay-like fracture of composite insulators.