Thickening rules of HPAM seawater solutions from the South China Sea with magnetic treatment were studied by apparent viscosity measurement. Shear resistance，anti oxidative degradation，magnetic memory effects and flooding property of simulated core of viscosified HPAM seawater solutions were also investigated. The results show that the viscosity of HPAM seawater solution with mass concentration of 2 000 mg/L increased from 14.2 mPa?s to 18.1 mPa?s under the conditions of magnetization temperature of 30 ℃，magnetic intensity of 60 mT，magnetization time of 1.5 h and magnetization speed of 800 r/min，and the thickening rate reached to 27.5%. Shear resistance to 50-200 mesh and anti oxidative degradation of viscosified HPAM seawater solution with magnetic treatment at 30 ℃ were obviously superior to those of untreated HPAM seawater solution at the same temperature. The magnetic memory time of the viscosified solution could last for 9 d.After HPAM seawater solution flooding，3.9 times the pore volume of simulated core of viscosified HPAM seawater solution with magnetic treatment were injected and the injection pressure was increased by 35 kPa. Therefore，the swept volume was improved and the oil efficiency was enhanced.