Due to the limitation of oil production platform，it is difficult to carry out thermal recovery in offshore heavy oil reservoirs by steam injection. The technology of multi-thermal fluid has a great potential to develop the offshore heavy oil reservoirs because of its small equipment size. A long sand-pack tube model was used to analyze the influence of injection temperatures and fluid component on oil displacement by multihermal fluid，and then a 2D physical simulation with the similar scale was carried out to study the production performance and the distribution characteristics of temperature field.Finally，the mechanism of oil displacement was summarized. The results show that the best injection temperature is 250 ℃ and the best gas and steam ratio is 1∶3 for the multi-thermal fluid flooding. During the flooding，the steam chamber gradually advances from injection well to production well in a triangle mode. The whole process of flooding can be divided into four stages：start-up，displacement，steam channeling，and erosion. Among them，the highest oil production is from the displacement stage. The main mechanism of EOR involves thermal viscosity reduction，oil mobility increasing due to the dissolution of CO2，the formation of foam-like fluid during the precipitation of CO2 to increase the flow resistance of the gas phase and to improve the movability of crude oil.