Coal seam gas injection displacement extraction is an effective measure to reduce the gas content of coal seam. The engineering parameter setting and actual working conditions of coal seam in the process of gas injection displacement will affect the effect of displacement extraction. In order to explore the influence of various factors on the effect of CO2 enhanced displacement extraction and the sensitivity relationship between various factors. Using COMSOL Multiphysics numerical simulation software, the model of gas displacement by CO2 injection in coal seam is established. The four factors of gas injection pressure, coal temperature, coal permeability and coal load are analyzed. The results show that the increase of gas injection pressure and permeability strengthens the displacement, and the increase of temperature and load weakens the displacement. The sensitivity of the factors affecting the amount of gas displacement is coal permeability > gas injection pressure > coal temperature > load. The influence of coal permeability on the amount of gas displacement is 5.97 times that of gas injection pressure, the gas injection pressure is 15.30 times the coal temperature, the coal temperature is 1.65 times the load. The order of displacement velocity sensitivity is coal permeability > gas injection pressure > load > coal temperature. Effect of permeability on displacement rate is 9.22 times of gas injection pressure, the injection pressure is 32.66 times of the load, load is 3.20 times of coal temperature. Therefore, in order to achieve better displacement effect in practical engineering, it can be considered from the perspective of increasing coal permeability and increasing gas injection pressure.