Abstract: During the production of a heavy oilfield in Bohai bay, water cut of part of production wells goes up quickly. Analysis of the main reasons of water cut increasing shows that the high oil viscosity, poor oil-water mobility ratio and heterogeneity lead to injected water breaking through along high permeability zones, which seriously affects the water injection development performance. To solve these problems, displacement profile control of weak gel is a more effective way. For actual needs of the offshore oilfield development, the experimentation of displacement profile control of weak gel is applied in well group. Key parameters that impact flooding effect of the gel system are optimized for increasing oil production and decreasing water cut. Results show that oil viscosity influences flooding effect of weak gel, as the viscosity increases, flooding effect becomes worse. In low water cut stage, the later the injectron of weak gel, the worse the flooding effect, and the greater the injection quantity, the better the flooding effect. Considering injection capacity and economic factors, injection quantity should be reasonable in actual production process. Success of weak gel injection test points out the direction of development for offshore heavy oilfield.