Abstract: Yanchang oilfield is characterized by low-porositylow-permeability,high formation water salinity and low recovery ratio,in view of these problems the application research of biological active oil displacement agent has been carried out,which introduces the technology of oil displacement mechanism.Through a series of performance test on the washing capacity,interfacial tension,salt resistance,resistance to calcium and magnesium,the displacement efficiency of oil displacement agent formula has been evaluated and selected,and the field application has achieved good production effect.