In order to improve the polymer flooding effect of class II reservoir in land B oilfield，taking the characteristics of target reservoir and fluid properties as the research object，the best injection parameters and injection methods suitable for the target reservoir were optimized by carrying out the indoor displacement experimental of heterogeneous core model in the layer. The experimental results showed that，with the increase of polymer molecular weight and solution concentration，the size of polymer molecular aggregates increased，the resistance coefficient and residual resistance coefficient increased，but due to the influence of core pore throat shear，the amplification of residual resistance coefficient gradually decreased. It could be seen from the oil displacement experiment that the influence of polymer injection viscosity on the production effect was as follows，gradient viscosity increasing > alternating viscosity changing > gradient viscosity decreasing > single high viscosity > single low viscosity. Among them，the oil recovery of gradient viscosity increasing，alternate viscosity changing and gradient viscosity reducing was enhanced by more than 20%，and the oil recovery of gradient viscosity increasing was the best，being of 24.2%. The influence of polymer injection rate on production effect was as follows，gradient speed increasing > single high speed > alternate speed changing > gradient speed decreasing > single low speed. Among them，the oil recovery of the gradient speed increasing and alternating speed changing was enhanced greatly，and oil recovery of the gradient speed increasing was 25.6%. Under the condition that the injection slug size was fixed，the increasing effect of oil recovery under different combination injection methods was as follows：speed increasing and viscosity reducing > speed decreasing and viscosity increasing，and the enhanced oil recovery under the combination of speed increasing and viscosity reducing was 28.6% . It could be seen that the combination of changing injection speed and viscosity at the same time in the process of injection was better than that of single changing speed or viscosity.