In view of the characteristics of low porosity, low permeability,high temperature and high salinity of reservoirs in block M of Daqing Oilfield,conventional surfactants cannot achieve good oil displacement effect.Therefore,a new type of surfactant SZ?11 was synthesized using maleic anhydride,ethylenediamine and long?chain alkyl bromides as monomers,and then mixed with non?ionic surfactant AEO?3.A new oil displacement system with higher temperature and salt resistant suitable for low permeability reservoir is formed,and its performance is evaluated.The results show that the prepared oil displacement system has good temperature and salt resistance.After aging at 140 ℃,the interfacial tension can still reach 0.008 mN/m.The system still has low interfacial tension in high concentration of sodium chloride (150 000 mg/L),calcium chloride (9 000 mg/L) and magnesium chloride (2 500 mg/L); the oil displacement system also has good emulsifying performance and wettability. The oil displacement efficiency can be improved by emulsifying crude oil and changing the wettability of rock surface. The oil recovery of reservoir core can be increased by 19.5% by injecting 0.4 PV prepared surfactant after water flooding step.The field application results show that after surfactant injection,the daily oil production of 5 production wells in block m is significantly increased,the water content is decreased, and better oil production increase effect is achieved.