A hydrophobically associating polymer flooding agent with high temperature resistance，salt resistance and good solubility in weak alkaline environment was exploited. A alkali-soluble hydrophobically associating terpolymer P（AM/AA/BEM） was synthesized by 2-（2-［4-（1，1，3，3-tetramethylbutyl）phenoxy］ethoxy）ethanol（OP-10）as emulsifier，acrylamide（AM），acrylic acid（AA）and behenyl polyoxyethylene ether methacrylate（BEM）as raw materials. The synthesis condition of P（AM/AA/BEM）was optimized and the performance of polymer solution was studied in detail. The results showed that the optimum reaction condition of P（AM/AA/BEM）was obtained as follows：20% total monomer mass fraction，25% AA mole fraction，0.2% BEM mole fraction， 0.3% initiator 2，2'-azobis［2-methylpropionamidine］ dihydrochloride （V50） mass fraction， 45℃ reaction temperature and 8 hrs reaction time. It showed good thickening property，heat resistance（90℃），salt tolerance（20 g/L）and shear thinning. There was strong synergistic effect between P（AM/AA/BEM）and sodium dodecylbenzenesulfonate（SDBS）. When 400 mg/L SDBS was added in 1 g/L P（AM/AA/BEM），the viscosity of hybrid system increased 3.3 times. P（AM/AA/BEM）showed better thickening property，heat and shearing resistance and salt tolerance than partially hydrolyzed polyacrylamide（HPAM）.