Abstract: This paper introduces the synthetic FP-1 cationi polymer anticlayswelling agent with good acid and salt-resisibility.Research results obtained by expansion instrument, capillary seepage time(CST),laser grain for analysis,scanning transmission electron microscope and core flow test show that it is a kind of good anti-clayswelling agent. It can be applied to treatment fluids of well completion,anti-swelling,fracturing and acidizing of injection and production wells. It has an important function for prolonging waterflood cycle and ensuring success in downhole operations such as perforation,acidization and fracturing.