In the middle of the last century,American scientists put forward the concept of capillary number and obtained the relation curve between capillary number and residual oil through experiments.They revealed that the corresponding residual oil saturation decreased with increasing of capillary number;after capillary number reached up to a limit,residual oil saturation would become stable and did not decrease.These important achievements laid a theoretical base for enhanced oil recovery with chemical flooding.On the basis of the theory,scholars developed chemical flooding numerical simulation software UTCHEM.During the numerical simulation study of combination flooding,the authors found that as the capillary number is higher than the limit capillary number,the changes of the residual oil saturation along with the capillary number differ from the classical capillary number curve.Oil displacement experiments prove that there are defects in classic capillary number experimental curve and it is necessary to mend and improve.Capillary number‘calculation’curve is obtained with a method of numerical simulation calculation and a complete description of capillary number curve is provided;On this basis,combination flooding capillary number experimental curve QL is obtained through experiments,which is different from the classical capillary curve;and based on which,an expression of corresponding combination flooding relative permeability curve QL is given and the corresponding relative permeability parameters are determined with experiments.Further oil displacement experiment research recognizes the cause of the singular changes of the capillary number curve.“Combination flooding capillary number experimental curve QL”and“combination flooding relative permeability curve QL”are written in combination flooding software IMCFS,providing an effective technical support for the application of combination flooding technical research. In the middle of the last century, American scientists put forward the concept of capillary number and obtained the relation curve between capillary number and residual oil through experiments. They revealed that the corresponding residual oil saturation decreased with increasing of capillary number; after capillary number reached. up to a limit, residual oil saturation would become stable and did not decrease. These essential achievements laid a theoretical base for enhanced oil recovery with chemical flooding. On the basis of the theory, scholars developed chemical flooding numerical simulation software UTCHEM.During the numerical simulation study of combination flooding, the authors found that as the capillary number is higher than the limit capillary number, the changes of the residual oil saturation along with the capillary number differ from the classical capillary number curve.Oil displacement experiments prove that there are defects in classic capillary number experimental curve and it i s necessary to mend and improve. Capillary number’calculation’curve is obtained with a method of numerical simulation calculation and a complete description of capillary number curve is provided; On this basis, combination flooding capillary number experimental curve QL is obtained through experiments, which is different from the classical capillary curve; and based on which, an expression of corresponding combination flooding relative permeability curve QL is given and the corresponding relative permeability parameters are determined with experiments. Fuurther oil displacement experiment research recognizes the cause of the singular changes of the capillary number curve. “Combination flooding capillary number experimental curve QL” and “combination flooding relative permeability curve QL” are written in combination with flooding software IMCFS, providing an effective technical support for the application of combination flooding technical research.