Isospin degree of freedom is introduced in Skyrme potential and momentum dependent interaction to obtain the revised isospin dependent quantum molecular dynamics. The isospin effect of isospin fractionation ratio is studied for different beam energies and different colliding systems based on the revised isospin dependent quantum molecular dynamics. It is found that the isospin effect of isospin fractionation ratios is important for different incident channel conditions，for example，the isospin fractionation ratios for different incident channel conditions are reduced after the isospin degree of freedom in Skyrme potential and momentum dependent interaction are included. However, the isospin fractionation ratio is also sensitive to symmetry potential. In this case it is also a good probe for extracting information on the symmetry potential in heavy ion collisions.