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Under the guidance of the carbon peaking and carbon neutrality strategies, the recovery, emission reduction, and effective utilization of industrial CO 2 are particularly important. Supercritical CO 2 viscosity reduction technology effectively improves the flowability and reduces the energy consumption of heavy oil pipeline transportation. This work reviews the experimental research on supercritical CO 2 viscosity reductions of heavy oil, summarizes the viscosity reduction mechanisms and main influencing factors, describes the research achievements regarding theoretical parameters such as the solubility and viscosity of supercritical CO 2 and the density and viscosity of live oil, introduces engineering applications of supercritical CO 2 in the oil and gas field, analyses the problems involved in corrosion, stability, and solids deposition of crude oil containing dissolved CO 2 , and presents the current challenges and perspectives. The main future research directions of this technology involve the mechanism of supercritical CO 2 viscosity reduction, ensuring the stability of supercritical CO 2 and crude oil mixtures during pipeline transportation, designing and establishing oilfield surface engineering facilities for supercritical CO 2 viscosity reduction technology, and improving the protection strategies for CO 2 corrosion. This work can provide a reference for the application of supercritical CO 2 in heavy oil development and pipeline transportation.