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CO2 miscible flooding is a key method to improve oil recovery. However, under most petroleum reservoir conditions, CO2 cannot achieve miscibility with crude oil. Therefore, reducing the minimum miscible pressure (MMP) between CO2 and crude oil has become a critical objective. This study investigated MMP reduction and CO2 displacement efficiency of miscibility-enhancing agent (MEA) using low-permeability artificial cores and reservoir oil samples from the Xinjiang Oilfield. A core displacement method was established to determine the MMP and, in parallel, to screen four candidate MEAs. Nuclear magnetic resonance (NMR) technology was employed to probe the pore-scale mechanisms by which MEAs reduce the MMP between crude oil and CO2. Results showed that, before adding an MEA, the baseline MMP of CO2–crude oil system was 21.38 MPa. Among the four MEAs, tributyl citrate (TC) exhibited the strongest effect, lowering the MMP by 1.61 MPa. TC concurrently improved CO2 conformance efficiency in both large pores and small pores, improving oil recovery during CO2 flooding. These results demonstrated that TC-enabled miscibility tuning offers a practical pathway to reduce MMP and improve CO2 conformance in low-permeability reservoirs. It provided a foundation for pilot-scale conformance control implementation in the Xinjiang Oilfield and analogous CO2 flooding reservoirs.