Abstract: Multiple thermal fluid technology is a technology to produce high temperature and high pressure stack gas after the burning of mixed fuel oil and air,meantime,to heat water and vaporize water,and produce multiple thermal fluids mixture with high temperature and high pressure,composed by nitrogen,carbon dioxide,water and etc,and inject the mixture into oil layers so as to improve oil production.Through the indoor experiment and numerical simulation,the action mechanism of the multiple thermal fluid technology to enhance heavy oil recovery has been made clear.As co2 is soluble in heavy oil,realizing viscosity reduction.Nitrogen is of energy-increasing and cleanup-addictive function,and it can enlarge the sweeping scope of steam and reduce hot loss in steam injection.Compared with hot water displacement,the multiple thermal fluid technology can increase 11.8%displacement efficiency.With the pilot testing of multiple thermal fluid technology application in Cao block,good oil increment has been obtained.