Abstract: After the polymer flooding, Daqing oilfield is characterized by developed preferential flow path, serious channeling and difficulties in efficient production. In order to maintain the sustainable and effective development of the oilfield, researches have been carried out for the technologies of profile modification, water plugging and flooding. Regarding the requirement of profile modification and water plugging, a viscosity-controlled gel system is developed. The initial viscosity of the system is less than 20 mPa·s, during 10~40 days, the system viscosity is less than 300 mPa·s and the gel viscosity is above 2 500 mPa·s. The data from cored wells after polymer flooding are used to design a physical model. The optimal injection volume determined by orthogonal experimental design is 0.10 PV, the injection concentration is 1 000 mg/L and the injection rate is 0.6 mL/min. The actual application shows that after modification the shunt rate of high-permeable layer reduces from 66.9% to 0.7%, that of medium-permeable layer increases from 33.0% to 85.0%, that of low-permeable layer improves from 0.1% to 14.3%. The system has low pollution to medium and low permeable layers and can effectively plug the high-permeable layer, which can meet the demands of field operation