Water plugging agent has been widely applied on oilfield EOR processes for decades. Conventional plugging agents used on reservoirs with low temperature (50 degrees C) and high salinity (28.6x10(4)mg/L) encounters with some limitations, such as slow gelling, weak gel strength, and poor instability. To overcome these problems, a novel acrylamide monomer polymer gel with strong gel strength, controllable gelling time and good stability was developed. The gelation processes of the plugging agent system at low temperature and high salinity is studied. The cross-linking reaction process of plugging agent is found to be in three stages: induction stage, rapid cross-linking, and stable stage. The composition of this plugging agent system is optimized: 5 similar to 7.5wt% acrylamide+0.5 similar to 0.75wt% cross-linking agent+0.005 similar to 0.12wt% retarder+0.5wt% initiator. The plugging rate is over 96.5% in high permeability sandpack. It also displays good shear resistance. With the continuous flooding by water after the gel is formed, the polymer gel shows good flooding resistance. It can block the water effectively until 10 PV of injected water.