In order to expand sources of surfactants used for oil displacement in oilfield，the biological oil sulfonate was synthesized from waste cooking oil by sulfonation. The influences of mass fraction of biological oil sulfonate，mass concentration of sodium chloride，total mass concentration of calcium and magnesium ions and temperature on the interfacial tension between biological oil sulfonate solution and crude oil were studied. The results show that the minimum interfacial tension between biological oil sulfonate solution and crude oil decreases with the increase of mass fraction of biological oil sulfonate. The minimum interfacial tension can be reduced to the ultra-low level when mass fraction of the biological oil sulfonate increases to 0.15%. The minimum interfacial tension between biological oil sulfonate solution and crude oil remains at ultra-low level with an increase of mass concentration of sodium chloride when the mass concentration of sodium chloride is less than 80 g/L. The minimum interfacial tension between biological oil sulfonate solution and crude oil maintains at ultra-low level with the increasing total mass concentration of calcium and magnesium ions when the total mass concentration of calcium and magnesium ions is lower than 400 mg/L. The minimum interfacial tension between biological oil sulfonate solution and crude oil decreases first and then increases with an increase of temperature. But the minimum interfacial tension keeps at ultra-low level with temperature under 70 ℃. Compared with petroleum sulfonate provided by Daqing Oilfield，the biological oil sulfonate has a better effect on reducing interfacial tension between oil and water at high mass concentration of sodium chloride，high temperature and high total mass concentration of calcium and magnesium ions.