Abstract: The oil reservoirs with developed natural fractures are faced with fast waterline advancing, easy water channeling and poor water flooding effect in the process of water flooding development. In order to solve these problems, Honghe Oilfield carried out researches and field tests on profile control technologies with gel plugging and gel plugging+particle/bentonite plugging. Due to the material mechanical performance of the gel system, however, the overall effect is not satisfactory. A series of investigation and analysis were carried out to select a set of high-strength plugging agent system of monomer polymerization. This system has the advantages of high viscosity, short gelation time, high strength and good thixotropy. Under the condition of 65 ℃, its gelation time is adjustable between 15 h, and the breakthrough pressure in the pipeline with length of 0.5 m and diameter of 3 mm is 7.0 MPa/m. In Honghe Oilfield, pilot tests are performed in four wells by five times and the effective rate is 100%. It can form high-strength plugging in fractures and effectively increases the plugging strength of the plugging agent in straightly-connected fractures. After profile control is implemented, average pressure is increased by 6.7 MPa, cumulative water injection is 5 643 m³ and cumulative oil increase is 2 723.1 t. In conclusion, this system can effectively solve the problem of fast water channeling in the oil reservoirs with developed natural fractures in the process of water flooding development in Honghe Oilfield.