Abstract: Compared with the common associating polymer, ultra high molecular weight association polymer is qualified with higher molecular weight and less association degree. So it has different viscosifying performance, viscoelasticility and microstructure. So a kind of common associating polymer with molecular weight 5 million and a kind of ultra high molecular weight associating polymer with molecular weight 19 million were chosen, through flow viscosity test device and Antonpar rheometer, the flow viscosity and viscoelastic behavior of the two kinds of polymer solution were tested. The results show that by the cooperative action of higher molecular weight itself and some degree of associating action between molecular chains, the ultra high molecular weight associating polymer could form higher flow viscosity during porous media seepage, and is qualified with higher Wiesenberger number under the steady shear conditions. Through the microstructure research with freeze-fracture scanning electron microscope, it shows that the ultra high molecular weight associating polymer has tighter network structure between chains. Finally the oil displacement result shows that compared with common associating polymer, it can enhance oil recovery effectively.