Abstract: In order to solve flue gas acid condensation problems in the thermal recovery of heavy oil，heat transfer calculation model of flue gas along the pipe were established on the basis of continuity equation，energy equation and momentum equation， the flue gas pressure distribution along the pipeline，the temperature distribution and the position of the flue gas acid dew point were calculated，the different components of flue gas and inlet parameter effects on gas pressure，temperature and the acid dew point in pipe were analyzed． The results showed that with the SO3 or water vapor content increasing，the temperature that flue gas acid dew began to appear higher， the distance between condensation point and inlet reduced; The pressure of inlet flue gas increasing，pressure drop became smaller，temperature drop remained 0. 5 unchanged，acid dew point tended closer to the pipe inlet; the higher gas inlet temperature，the bigger pressure drop and temperature drop，the farther from the entrance to the acid dew point position; When insulation layer thickness increasing，the temperature drop decreaseed，and the distance gas start to condensates increased． Calculation and analysis results showed that the reducing SO3 or vapor content in the flue gas could effectively increase the acid dew point distance，reduce the pipeline corrosion problem．