Abstract: Polymer flooding is an effective tertiary oil recoverymethod to improve effects of waterflood development.Commercial application of polymer flooding have beencarried out in Shuanghe and Xiaermen oilfields of HenanPetroleum Exploration Bureau leading to large amount ofincrease in oil production. Daily oil out put increase,water-cut decrease,the estimated term of validity ofpolymer flooding is 8 years and incremental oil recoveryis 9%. Economic evaluation shows that the net presentvalue of polymer flooding remarkably increase comparedwith that of water flooding and unit production costdecrease. The investment effectS of polymer flooding arehigher than that of progressive exploration and alsohigher than that of well pattern thickening in latedevelopment period. In case that progressive explorationhave no large discoveries and spaces for thickening wellpatterns get srnaller and smaller, commercial applicationof polymer flooding should be strengthened to slow downdecline of oil production and stabilize the development ofHenan oilfield.