The surface material of composite insulators has good electrical performance and high mechanical strength, and in recent years, the pollution flashover accident rate has been well controlled. However, during maintenance and operational testing, it is still common to find electric marks or abnormal temperature rise on the surface of insulators. The external temperature of the surface during arc discharge can be obtained through infrared thermal imaging, which is also one of the most commonly used detection methods for power equipment in current engineering. During operation and maintenance, infrared detection of surface temperature rise is used to determine whether there is or may be abnormal discharge in the insulator, but the temperature rise inside the insulator cannot be determined. This article refers to the core rod diameter and sheath thickness parameters of actual suspension composite insulators, and designs an experimental research model for the laboratory. We conducted an interior temperature detection test on the surface of the test sample for contamination discharge and measured the leakage current during the process. At the same time, the electric field intensity distribution of the plate model embedded with the Fiber Bragg gratings (FBGs) was simulated. The results indicate that the grating temperature sensor implanted inside the silicone rubber (3mm) can detect the temperature rise of the surface contamination discharge of the silicone rubber, and the field strength of the flat model was not distorted. The arc starting electrode was consistent with the simulated field strength distribution. When the distance between temperature measuring points is less than 31. 5mm, the temperature distribution of the inner interface of 3mm thick silicone rubber is basically consistent, that is to say, the grating spacing should be greater than 31. 5mm when actually making the fiber grating composite insulator.