The present invention is a kind of chemical oil displacing agent for the third oil exploitation.

The oil displacing agent consists of sodium octyl benzene sulfonate as anion surfactant 40-65 wt%, surfactant assistant 10-20 wt%, surfactant synergist 5-11 wt% and surfactant solubilizing assistant 3-9 wt%. The oil displacing agent can raise the moistening and penetrating capacity of injected water, improve water absorbing property of oil reservoir, raise the affected range of water in oil displacing, lower the structural viscosity of condensed oil, reduce the flow resistance of oil in stratum, and reduce the tension in the interface between oil and water to raise oil washing efficiency and oil exploitation efficiency. In addition, it is pollution-free.