Due to a good injectivity and high oil-flooding capacity, CO₂ flooding has become a very potential method to improve oil recovery in low permeability / tight oil reservoir, but influenced by reservoir heterogeneity and fractures, gas channeling easily happens during the injection affecting the development of reservoirs. The joint CO₂ flooding and huff-n-puff experiments were designed and conducted in core with different permeability contrast, and oil recovery and oil distribution (scanned by CT) was measured as the index to investigate the effect of heterogeneity on CO₂ flooding. The results show that, during the continuous injection of CO₂, as the permeability contrast increases from 1.0 to 2.2, the oil recovery is significantly reduced from 88.5% to 58.3%; when this contrast further increase from 2.2 to 154.0, the decreasing trend of oil recovery slows down from 58.3% to 44.8%. The distribution of residual oil shows that the injected CO₂ mainly flows in