Fractures and leakage paths lead to reduced oil recovery during production from hydrocarbon reservoirs. Waterflood can not sweep oil from low permeability zones which contain unswept oil. Polymer microgels can minimize this issue during flooding process by blocking high-permeability zones, specially fractures and diverting waterflood to low permeability zones. These polymers can swell several times as pH increases. At low pH, the viscosity of polymer’s solution is low so it can be placed deeply into the high permeability zones of reservoirs. As a result of reaction between polymer and rock minerals or cement(behind pipe) within reservoirs, the polymer viscosity increases so water flood could be diverted from high permeability zones to low permeability zones. To measure rheological properties of polymer solution, laboratory experiments is conducted. The properties like yield stress, viscosity are measured for different polymer concentrations and for different salinity as a function of pH. For the next step,a mathematical model is developed to predict the behavior of pH-sensitive polymer. The model is applied at the reservoir to verify the leakage issue.