Abstract: Oil and water percolation properties can be improved and water permeability can be increased through changing interfacial tension between oil, water and rock, so as to lower injection pressure in low permeability reservoir. Experimental study of depressurization and augmented injection with surfactant of low concentration is carried out in several low permeability oilfields. Laboratory experiment results show that injection pressure can be lowered to some extent through injecting surfactant into core, with the maximum value of reduction in the range of 40% -60%.