Suizhong oilfield is an offshore heavy oil one. The ground density of crude oil is between 0.958 and 0.982 g/cm3.The underground viscosity of crude oil is between 50 and 250 mPa?s. In order to decrease water breakthrough，to enhance oil recovery and to improve development effect，polymer flooding pilot test was put into practice in 2003. Enhanced liquid treatment was implemented fully in high water cut block in 2010，and subdivision of layer series was put into practice in 2013. With the implementation of various measures，it is difficult to distinguish incremental oil effect of each measure.Analogy method was used to evaluate polymer flooding effect. The new water cut forecasting model was derived based on relative permeability curve and material balance theory. By comparing the predicted water cut curve with the actual water cut curve，the turning point of the curve is response time，and the difference value of the curve is oil increment of polymer flooding. Incremental oil of various measures was calculated by dynamic method and numerical simulation method，which realizes the splitting of incremental oil from polymer flooding，integral liquid increase，subdivision of series of strata and other stimulation measures. By the end of 2015，the cumulative incremental oil of polymer flooding is 264.3×104 m3，that of integral liquid increase is 97.1×104 m3，and that of subdivision of series of strata is 12.6×104 m3.