Abstract: A cationic polymeric thickening agent used in fracturing fluid was developed for use in formations of middle or high temperature. Analyses of the thickening agent using IR spectrum, NMR and SEM showed that a spatial network was formed by the molecules of the polymer after reacting with an electric-attraction inducer, rendering the polymer very good thickening capacity. This polymer has viscosity between 40-55 mPa·s after shearing at 170 s^-1 at 110℃ and 130℃ for 1 hour. Time for gel breaking was 71.5 minutes at 90℃. No residue was left after gel breaking, meaning that reservoir damage caused by this polymer would be very low (12.7% in an experiment.) Fracturing fluid formulated with this polymer showed very good viscoelasticity, and sand carrying capacity, rate of sand sedimentation being 1.96×10^-4 m/min. At normal temperature, fracturing fluid containing 60% sands still showed good suspension stability after standing for 1 hour. As a cost-effective material, it satisfied the need for field fracturing operation, as shown in the fracturing of the lower segment of HE-8 in Well Su20-23-X, Sulige gas field.