In order to prepare the fracturing fluid with good heat resistance， a acrylamide copolymer thickening agent PAS-1 was prepared using acrylamide and acrylic acid as backbone monomers and sulfonic acid group monomer、 cationic monomer and long hydrophilic chain monomer as functional monomers. The best synthesis conditions were optimized by investigating the effect of the monomer proportioning and reactive conditions on its performance. The structure of the copolymer was characterized and the major performance of the formed fracturing fluid was evaluated. The optimization of experimental conditions was concluded as follows: the mole ratio of AM， AA， PSN， AP and DMDAAC was 4.5∶2.5∶0.80∶0.0040∶0.18；the initiator ammonium persulfate（APS） concentration was 0.8%；and the reaction was initiated at the temperature of 40℃ for 30 min and continued at the temperature of 60℃ for 24 h. The thickening agent PAS-1 had xcellent thermal stability at the high temperature within 300℃. The thickening agent PAS-1 had strong ability of increasing viscosity， and the viscosity of the PAS-1 solutions was up to be 43.7 mPa·s at the mass fraction of 0.6%. the sedimentation velocity of the proppants was 0.095 mm/min when the proppants was placed into the fracturing fluid containing 1% PAS-1 and 0.6% cross-linking agent SJ66， indicating that the fracturing fluid prepared by thickening agent PAS-1 had excellent sand-carrying ability. The final viscosity of the formed fracturing fluid system was above 50 mPa·s after continuously shearing for 120 min at the speed of 170 s^-1 and at the temperature of 200℃ ， possessing a good performance of temperature tolerance and shearing resistance. Therefore， the thickening agent PAS-1 could meet the performance requirements of high temperature fracturing fluid.