Abstract: Tight reservoirs are poorly developed by water flooding due to low permeability, small porosity, and extensive development of micron and nano pores. The use of CCUS-EOR technology can realize the geological sequestration of CO₂ in the reservoir while improving the crude oil recovery efficiency. Currently, research on CO₂ sequestration mechanisms primarily focuses on saline aquifer sequestration, with less emphasis on adsorption and sequestration during CO₂ flooding in tight oil reservoirs under water containing conditions. To address the above problems, this paper constructs a pore wall model for tight reservoirs using hydroxylated quartz cells based on molecular simulation methods, establishes the fluid components of CO₂, crude oil short chain alkanes and water, respectively, and investigates the competitive adsorption characteristics of CO₂ and crude oil short chain alkanes under water containing conditions. The results show that under water containing conditions, the adsorption isotherms of each component during the competitive adsorption of CO₂ and CH₄, CO₂ and C₂H₆ are in accordance with the class I adsorption isotherm, and the absolute adsorption amount, excess adsorption amount and heat of adsorption of CO₂ are larger than those of CH₄ and C₂H₆. The adsorption of CO₂ and crude oil short chain alkanes on the quartz wall is physical adsorption. Under simulated conditions, the number of water molecules has a significant impact on the adsorption amount of CO₂ and a relatively small impact on the adsorption amount of CH₄. An increase in the proportion of CO₂ will lead to an increase in its adsorption amount and a decrease in CH₄ adsorption amount. An increase in temperature will reduce the absolute adsorption amount of CO₂ and CH₄. An increase in pore size also increases the absolute and excess adsorption amounts of both CO₂ and CH₄. The type of wall mineral has a significant impact on the adsorption capacity of CO₂ and CH₄.