Abstract: In order to realize the real-time monitoring of the downhole temperature in the whole cycle of steam huff and puff in BoHai Oilfield, FBG and DTS Mutual correction theory are applied, and the method of externally bundling and sealing the inner tubing of the above oil pipe is adopted to realize temperature monitoring of all wellbore. The test shows that the monitoring technology, the monitoring technology has a spatial resolution of 0.5 m and a temperature measurement accuracy of 1℃. Under the premise of satisfying the temperature resistance level and monitoring accuracy, the safety of the cable can be effectively guaranteed.This technology is mainly used for long-term real-time monitoring of the whole wellbore temperature, oil jacket annulus and horizontal section temperature of thermal recovery wells in Bohai Oilfield. Taking L well as an example, the application range of the technology is analyzed, and the application effect and monitoring data are analyzed. The maximum temperature of the bottom hole during the steam injection was measured at 368.2℃. It is the first time to realize real-time monitoring of all wellbore temperature in the annulus and horizontal section of thermal production Wells in BoHai Oilfield.