Abstract: Shale reservoir has tight rock, small pore throat and very low permeability. How to enhance the permeability of shale is the key to improving the recovery rate of shale oil and gas. Through conducting liquid nitrogen (LN₂) low-temperature treatment experiments on shale cores and cyclic injection of CO₂ flooding experiments, the effects of cyclic gas injection at different injection pressures after LN₂ low-temperature treatment on the recovery rate of shale oil, core physical properties, and relative permeability of oil and gas phases were studied, and the changes in the microscopic pore structure before and after the treatment were clarified. The experimental results show that after LN₂ injection, the shale can generate a thermal stress of 313.5 MPa, inducing the formation of micro-fractures. The volume expansion effect of LN₂ vaporization and cyclic CO₂ flooding can form a re-pressurization mechanism in the core after the formation of micro-fractures, expanding the induced fractures and improving the permeability. The recovery rate of CO₂ flooding is proportional to the injection pressure. The cumulative recovery rates of the first and third rounds of supercritical CO₂ flooding are 32.4% and 34.9% higher than those of subcritical CO₂, with an increase of 154.6% and 101.7%, respectively. The number of required flooding cycles for high-pressure CO₂ injection is reduced, and the produced oil mainly comes from the first two rounds of flooding. Compared with the initial shale core, the porosity after supercritical CO₂ cyclic flooding increases by 78.6%, the permeability increases by 27,204%, the average pore diameter increases by 176%, and the maximum relative permeability of oil and gas increases by 1.8 times and 2.3 times, respectively. The research results provide a reference for the production increase of shale oil and gas.