Due to the complex formation conditions，serious heterogeneity，the development of natural or artificial fractures，and adverse mobility ratio of CO2，thus CO2 gas channeling is serious and the recovery factor is low. In order to reduce the gas mobility and improve the effect of CO2 flooding，YC oilfield provided a linear block copolymer thickener based on the property of CO2. The shear rheological property，high temperature and high pressure rheological property of the thickener/CO2 system were evaluated by simulating YC oilfield block. Combined with two-dimensional core and three-dimensional triaxial model experiments，the oil displacement effect of thickener/CO2 system was evaluated dynamically. The results showed that the system formed by thickener and CO2 had good stability at 40—80℃，which could increase the viscosity of CO2（0.014 mPa·s）by about 20 times. Temperature had little effect on the viscosity of thickener/CO2 system. As the shear rate increased，the viscosity of thickener/CO2 system decreased. While as the pressure increased，the viscosity of thickener/CO2 system gradually increased. Under simulated formation conditions，the thickener/CO2 system had a good effect on reducing CO2 mobility and improving gas flooding. For heterogeneous cores，the enhanced recovery factor（13.75%）for cores with small permeability differences was greater than that（11.98%）for cores with large permeability differences. For homogeneous cores，the thickener/CO2 system could effectively improve the problem of serious CO2 channeling，further develop CO2 displacement effect and greatly increase the recovery factor of crude oil.