In order to ensure the accuracy of high temperature distributed temperature measurement in oil and gas wells, a high temperature single mode Raman self-calibration monitoring system is designed. The working principles of the distributed Raman temperature measurement system and the fiber grating temperature calibration system in the system are introduced, and the high temperature monitoring experiment of 800 ℃ is carried out for the temperature measurement range and accuracy of the system. The experimental results show that the temperature resolution of the system is 0.1 ℃ and the temperature measurement accuracy is ± 2 ℃ under the condition that the temperature measurement distance is 0~1 km and the temperature range is 0~800 ℃, which basically meets the requirements of high temperature distributed temperature monitoring.