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When injecting polymer into an oil reservoir, polymer adsorption onto the grain surface may seriously clog the pore throat and decrease the permeability. This phenomenon may give rise to a severe cross-flow problem in the case of a layered reservoir with a large permeability contrast. Therefore, we proposed a remedial method, which injects polymer solution with different concentrations under the same condition of the frontal velocity at each layer, to overcome the cross-flow problem. In order to perform this task, the experimental system was built as a two-dimensional two-layered sandstone system with a large permeability contrast of 10. From the results of the experimental investigation, conventional polymer flooding was found to be inefficient in oil recovery, because of the cross-flow problem that occurred almost from the beginning of injection. Meanwhile, in the case of the suggested remedial method of polymer flooding, the oil production was significantly enhanced without showing the cross-flow problem, which was accomplished by injecting the polymer solution with different concentrations under the conditions of the same frontal velocity at each layer. Overall, the suggested injecting method was found to be sufficient to overcome the cross-flow problem in a layered reservoir.