Abstract: In order to study microscopic damage mechanism of asphaltene deposition on reservoirs with different permeabilities during CO₂ flooding, cores with high, medium and low permeabilities are selected for indoor CO₂ flooding experiments and plugging degree of pore throat in cores are analyzed quantitatively by using NMR technology. The experimental results show that the deposition rate of asphaltene during miscible phase stage is obviously higher than that during immiscible phase stage, and the deposition rates are basically same in the cores with different permeabilities; permeability damage rate is positively correlated with the asphaltene deposition rate and the larger the core permeability, the smaller the permeability damage rate; the pore throats in low-permeability cores are blocked seriously with the plugging rate of relatively small pore throats (0.01~1 ms) reaching 38.19%, the plugging rate of relatively small pore throats in high-permeability cores is only 9.59%, which is significantly lower than the previous one