Heavy oil reserves in Xinjiang oilfields are abundant，and the main development methods at the present stage are still steam stimulation and steam flooding. However，the oil-steam ratio and oil production are lower at the middle and late development stages. In order to improve the recovery rate，it is urgent to change development method. In this paper，the M-zone crude was taken as the research object，the oil-displacement efficiency of immiscible steam-CO₂ flooding relative to the pure steam flooding in the high-permeability and low-pressure oil reservoirs and the steam-CO₂ in different residual oil saturations were studied systematically through laboratory experiments. The results showed that when the development method changed to steam-CO₂ flooding from steam stimulation after a certain time，the oil displacement efficiency increases by 34.1%. The steam-CO₂ flooding had the gas and water alternating flooding characteristics. If CO₂ was injected too early，the percolation channel would be opened in advance. The steam would contact most of the crude oil in the tunnel prematurely，which resulted in that the crude oil was emulsified and some emulsified crude oil was difficult to be swept out. When the residual oil saturation was 45%，the final oil displacement efficiency could reach up to 87% ，which was the best CO₂ injection opportunity in the experiment. However，in the actual development process，the CO₂ injection opportunity should be determined through judging whether the steam channel was open by the water production rate.