Abstract: CO₂ miscible flooding is complex, including mass transfer, convection, phase transition and other issues. Some mechanisms are not clear and need in-depth study. The static characteristics of n-pentane or crude oil and CO₂ in different phases were studied by using a CO₂ miscible flooding visual device under different experimental pressures. CO₂ and n-pentane or crude oil show different contact characteristics under different pressures. The relationship between n-pentane or crude oil relative height and time is a power function, and the curve at low pressure can also be approximately linear. The dissolution swelling rate of CO₂ vs. n-pentane or crude oil under different pressure conditions shows a decreasing trend with time, and the curves are negative logarithmic. The factors influencing the relative height of n-pentane or crude oil and the dissolution swelling rate of CO₂ vs. n-pentane or crude oil are mainly pressure and fluid properties.