Class II?B reservoirs have become the main exploitation target in Daqing Oilfield, and their geological reserves account for 45.8% of the Class II reservoirs.In view of the huge difference in the exploitation of Class II?B reservoirs,a two?phase mathematical model of viscoelastic polymer solution and crude oil was built,and the logarithmic conformation method was used to transform the model.The VOF method was employed to track the two?phase interface in the displacement process,and thus a two?phase numerical model of viscoelastic polymer solution and crude oil was obtained.Moreover,the effects of pore structure and viscoelasticity of polymer on microscopic oil displacement efficiency were studied by the microscopic model of Class II reservoirs. The results demonstrate that higher reservoir heterogeneity is accompanied by lower microscopic oil displacement efficiency,and the oil displacement efficiency of Class II?A reservoirs with better pore parameters is 2.10% higher than that of Class II?B reservoirs.With the increase in viscosity,the microscopic oil displacement efficiency increases,and the oil displacement efficiency of schemes with a viscosity ratio of (viscosity ratio of polymer to crude oil) 1.5 : 1,2.0 : 1 and 10.0 : 1 is 0.59%,0.80% and 4.10% higher,respectively, than that with a viscosity ratio of 1.0 : 1. With the increase in elasticity, the microscopic oil displacement efficiency rises, but when the elasticity is higher than 13 s,the microscopic oil displacement efficiency decreases slightly,which indicates that the elasticity of polymer solution has an optimal value for improving oil displacement efficiency.The research results provide important theoretical support for the polymer flooding development of Class II?B reservoirs in Daqing oilfield.