Whether CO₂ flooding could mix with crude oil under reservoir conditions directly affected the oil displacement efficiency. Therefore the miscible conditions between CO₂with crude oil and the minimum miscible pressure in miscible region were studied systematically in low permeability reservoirs. Selecting the low permeability target block in YC oilfield and under the simulated reservoir conditions，CO₂ flooding effects were acquired through the various series of experiments considering permeability，recovery，displacement velocity，gas-oil ratio，permeability differential as well as flooding pressure by flooding experiment in both homogeneous and heterogeneous rectangular cores. The method to determine the minimum miscible pressure by core experiment was established. The results showed that the method had good repeatability and could simulate low permeability or ultra-low permeability porous media and reservoir heterogeneity. The minimum miscible pressure was 18.5 MPa under the simulated reservoir conditions，which was the same as the calculation result of numerical simulation software and was 0.7 MPa higher than that of the traditional slim tube experiment. It reflected the consistency with two methods for the minimum miscible pressure. The effect of different factors，such as permeability，heterogeneity and displacement velocity on the minimum miscible pressure by core displacement experiment were studied. The core displacement experiment method could be used to determine the minimum miscible pressure in near-miscible region，which could deepen the mechanism realization of CO₂ near-miscible flooding and offer technological base and theoretical guidance for field application