Abstract: The effect of polymer，such as partially hydrolyzed polyacrylamide，on the dynamic and equilibrium interfacial tension of petroleum sulfonates and oil/water systems is examined.It is testified that polymer added in a certain concentration scope in the system only prolongs the time which the system needs to reach at the equilibrium interfacial tension，but the ability of the system for washing oil is not influenced.The simulation test by changing the injection sequence or injection mode of polymer and petroleum sulfonate indicates that the maximum oil displacement efficiency is acquired by the injection mode in which the petroleum sulfonate solution is injected after polymer flooding.The main reason is the decrease of adsorption site on the surface of rock for the adsorption of partially hydrolyzed polyacrylamide by hydrogen bond and the reduction of association body formed by polar group，so the loss of petroleum sulfonate in the core is decreased，as a result，the oil displacement efficiency of petroleum sulfonate for enhanced oil recovery is relatively increased.

Key words: residual polymer, petroleum sulfonates, equilibrium interfacial tension, adsorption loss, association body, displacement efficiency