The present invention provides a method for describing the heterogeneity of a carbon dioxide drive reservoir layer. The method comprises: Step 1, calculating the permeability difference of blocks, anddetermining a reasonable permeability differential limit according to the permeability difference of study areas; Step 2, processing a permeability interpretation result in a certain study area and calculating the permeability difference of a grid model; Step 3, using a numerical simulation means to study the influence of different methods on the carbon dioxide drive gas breakthrough time; Step 4, analyzing the influence of physical and chemical properties of crude oil in the carbon dioxide drive on the ratio of gas to oil; Step 5, using the numerical simulation means to analyze the flow difference of different permeability value models; and Step 6, using the ratio of gas to oil in the actual model to fit, compare and correct the average permeability value. By virtue of the construction method provided by the present invention, according to the parameters that can be provided in the numerical simulation, a method for discretizing the permeability curve is established, and a numericalsimulation basis is provided for the improvement of the numerical simulation accuracy of the carbon dioxide drive and the quantitative characterization of the displacement mechanism thereof.