Oil from more than 40 reservoirs in the Daqing oilfield has been effectively recovered using polymer flooding as a tertiary oil recovery method, with an average oil recovery factor of more than 50%.However, the heterogeneity of reservoirs causes low sweep efficiency in layers with poor properties and excessive polymer injection in layers with good properties.Polymer injection must be optimized to the layers according to the reservoir heterogeneity.Therefore, a laboratory experiment under formation pressure gradient conditions was conducted with artificial 3D heterogeneous models (length of 30cm, width of 30cm), and the 4 typical models used included both injection and production wells located at thick layers, injection wells at thick layers and production wells at thin layers, injection wells at thin layers and production wells at thick layers, and injectionand production wells at thin layers;the permeability between the injection wells and production wells varied between 300 ×10-3μm2 and 800×10-3μm2 , and the thickness varied between 2.25cm and 4.5cm.In the experiment, the model was water flooded to a comprehensive water cut of 94%, and then the polymer solution was injected to a water cut of 98% in each layer.The polymer injection was optimized based on the incremental recovery and incremental recovery per ton of polymer.The results show that the highest liquid production was observed in the model in which both the injection well and the production well were located at thick layers, so it is recommended that polymer plugging materials, such as gels, be injected into layersthat already have good properties, and slice mining be implemented in layershaving poor properties.A suitable injection amount clearlyexists for each layer, whether it is thick or thin.The optimized polymer injection amounts for the four models were 740PV · mg/L, 780PV · mg/L,810PV · mg/L and 860PV · mg/L, respectively.