Bohai oilfield is a typical conventional heavy oil reservoir, its water flooding recovery efficiency of this type oilfield is quite low, but the potential is great for polymer flooding. Because of the life limit of offshore platform and the risk of development investment,the offshore oilfield polymer flooding should focus on the word of“early”. The feature of injection of early polymer flooding is different from onshore polymer flooding in middle and later period. Reservoir model was established based on related data of typical Bohai heavy oilfield, and the injection timing and pressure feature were studied by numerical simulation techniques. A mathematical model of injection pressure of polymer flooding with influence factors was constructed, the key influence factors were obtained for injection pressure of polymer flooding, including reservoir permeability, oil viscosity, polymer injection timing, etc. Early polymer flooding injection time exists a critical value, and if injection time was greater than the critical value, the injection pressure would increase significantly. The results can provide reference and technical support for the early polymer flooding application of offshore oilfields.