Water plugging is an important means for the field to stabilize oil production and to control water cut. Due to the complexity of the formation, the plugging agent needs salt tolerance and washing stability. A swellable type blocking agent was synthesized by copolymerizing using acrylic acid (AA), acrylamide (AM), 2 - acrylamido - 2 - methylpropane sulfonic acid (AMPS), and acryloyloxyethyl trimethyl ammonium chloride (DAC) as monomer, N, N-methylene-bis-acrylamide (MBA) as a cross-linking agent. The effects of reaction conditions on the properties were studied and the optimal synthesis conditions were determined as follow: mass ratio of AA to AM was 4:1, the reaction temperature was 60 ℃, the amount of initiator, cross-linking agent, AMPS, DAC and MBA were 0.5% , 0.05%, 7% and 4% separately. The blocking agent had good salt tolerance and hardly expanded in kerosene. Plugging ability and resistance to scour of the plugging agent were evaluated by core flow tests and the plugging agent plugging rate reached 86.1% and injection pressure decreased slightly, after more than 25 times pore volume subsequent water scouring. The blocking agent had a strong resistance to erosion capacity.