The invention discloses a replay protection device which comprises a relay protection device body, a temperature measuring unit, a sampling maintaining unit and an analogy to digital conversion unit. The relay protection device body comprises a central processing unit. The temperature measuring unit comprises a temperature sensor, and the temperature sensor is arranged at the position of the relay protection device body. The input end of the sampling maintaining unit is connected with the output end of the temperature measuring unit, and the sampling maintaining unit conducts sampling maintaining on voltage signals output by the temperature measuring unit. The input end of the analogy to digital conversion unit is connected with the output end of the sampling maintaining unit, and the analog to digital conversion unit conducts analogy to digital conversion on the voltage signals output by the sampling maintaining unit. The output end of the analog to digital conversion unit is connected with the central processing unit, and the central processing unit calculates the temperature of a part of the relay protection device to be subjected to temperature measuring according to the digital voltage signals output by the analog to digital conversion unit. The relay protection device can achieve work temperature measuring and monitoring of key parts.