Abstract: Some related research findings show that an appropriate surface active agent can reduce the injection pressure of low permeability reservoir. The average reduced rate of 8 samples is 26. 6% and the enhanced displacement efficiency is 6.7%. After the solution action of surface active agent, the phase permeability curve changes obviously:the relative permeability of oil and water raises, two- phase flow domain becomes wider, and rock wetta-bility drifts towards the hydrophilic direction. The result shows that the compound 2# surface active agent is able to improve the waterflooding of Baolang oilfield which has low peamibility.