Paralleled cores flooding experiments were carried out to evaluate effect of foam flooding after polymer flooding under different water cut. The experimental results showed that polymer flooding followed by 0.3 PV foam slug could improve additiona l9.9% oil recovery. The larger size of foam slug was，the more enhanced oil recovery could reach. The oil recovery in the polymer flooding followed by more 0.5 PV foam slug increased by 6.9% than that in the polymer flooding followed by 0.3 PV foam slug，or 16.3% more than that in the polymer flooding only. When the foam was injected at different high water cut stage after early polymer flooding，the higher the water cut was，the greater the oil recovery increased. Followed by same foam slug injection size（0.3 PV），when 85% and 98% water cut was reached respectively，it was found that oil recovery in the polymer flooding could increase by 9.9% more. The results showed that the water cut stage had an important influence on the stability of the foam. The later foam was injected，the weaker crude oil defoaming effect was in the high permeability layers，the foam would be more stable and stronger，effective time of resistance retaining would be longer，the low permeability layers would be better exploited.