CO₂ foam flooding，as an enhanced oil recovery technology integrating the advantages of chemical flooding and gas flooding，significantly enhances crude oil production in complex reservoirs by synergistically utilizing the interfacial modulation capabilities of surfactants and the mobility control characteristics of CO₂. In recent years，it has demonstrated substantial potential in the development of unconventional oil and gas reservoirs，including heavy oil，shale oil，and tight oil. This paper reviewed the principle and influencing factors of CO₂ foam stability，the methods to improve the stability of CO₂ foam，the enhanced oil recovery mechanism under CO₂ foam flooding，and its application in unconventional oil reservoirs such as heavy oil and shale oil. Firstly，the principle of CO₂ foam stability was fundamentally governed by the following factors：the structures and properties of the liquid film， including drainage dynamics and gas diffusion rates； the hydrophilic-lipophilic balance of surfactants， and the Gibbs-Marangoni effect induced by interfacial tension gradients at bubble surfaces. Then，the effects of reservoir environments such as temperature，pressure，salinity，and crude oil on the stability of CO₂ foam were analyzed. The increase in temperature and salinity had an adverse effect on the formation and stability of foam. The rise in pressure had a positive impact on CO₂ foam stability. The light and heavy components of crude oil had different effects on foam stability. The methods of polymers，ionic fluids，nanoparticles，and the synergistic effect of surfactants and nanoparticles were proposed to improve the stability of CO₂ foams. Finally，the enhanced oil recovery mechanism of CO2 foam flooding was explained：the foam selectively blocks in the porous medium through the Jamin effect to improve the sweep efficiency，achieve crude oil emulsification/viscosity reduction，reduce the oil-water interfacial tension，change wettability，improve the mobility ratio of oil phase and displacement phase，and increase the fluidity of crude oil. Based on this enhanced oil recovery mechanism，the application of CO₂ foam flooding in unconventional oil and gas reservoirs for enhanced oil recovery（EOR）is summarized.