Abstract: The interaction between CO₂ and crude oil in micro-nano pores is a decisive factor determining the crude oil development effect, which is directly influenced by the injection and discharge method of CO₂ huff and puff. Based on the combined use of nuclear magnetic resonance and molecular simulation, the paper systematically investigates the law of the interaction between CO₂ and crude oil under different injection and discharge methods and its influencing characteristics on oil development, and analyzes the micro dynamic evolution process and molecular mechanism of crude oil during CO₂ injection huff and puff. The findings show that under the same pressure change conditions, linear pressurization injection can achieve better effect of interaction between CO₂ and crude oil than pulse pressurization injection, and sufficient convective mass transfer effect enable CO₂ and crude oil to dissolve and be miscible with each other. Through comparison of the crude oil recovery before and after huff, it is found that linear depressurization is more efficient in carrying and discharging crude oil than pulse depressurization extraction. The recovery rate of the injection and discharge combination experiment of linear pressurization and linear depressurization is 37.52 % , which is higher than 32.49 % achieved by the combination of injection and discharge through pulse pressurization and pulse depressurization. In addition, a micro mechanism model has been established for the interaction between CO₂ and crude oil during gas injection huff and puff, and the intermolecular forces and dissolution characteristics between CO₂ and crude oil have also been clarified. Under linear pressurization injection and linear depressurization extraction, the solubility promoting effect of CO₂ - crude oil is better, the number density value of CO₂ - crude oil intersection points is higher than that of pulse pressurization injection and pulse depressurization extraction, while the difference in solubility parameters is lower than that of pulse pressurization injection and pulse depressurization extraction, showing better miscible characteristics and crude oil stripping effect.