The aggregation behavior of asphaltenes significantly affects the viscosity of heavy oil. Studying the aggregation behavior of CO₂ on asphaltenes in heavy oil can further analyze the action mechanism of CO₂ in the process of displacement. Under different CO₂ pressures and conditions，CO₂ dissolution experiments were carried out on heavy oil and heavy oil containing CO₂ solubilizers （benzene or ethanol）. After separating the four components，CO₂-treated asphaltenes were obtained. X-ray diffractometer，scanning electron microscope and transmission electron microscope were used to characterize the interlayer spacing，surface morphology and microstructure of asphaltene aggregates extracted under different experimental conditions. The influence mechanism of CO₂ on asphaltene aggregation behavior in heavy oil was analyzed. The results showed that the dissolution of CO₂ in heavy oil broadened the layer spacing of asphaltene accumulation and retarded the aggregation behavior of asphaltene molecules. Solubilizers increased the concentration of CO₂ in heavy oil. It played a synergistic role to further decline the aggregation probability of asphaltene molecules in heavy oil，decrease the aggregation rate of asphaltene and diminish the interaction with glial molecules，thus reducing the viscosity of heavy oil.