The surface tension of surfactant aqueous solutions and dynamic interfacial tensions (DIT) between Shengli Oilfield crude oil and solution of octyl methylnaphthalene sulfonate surfactants (OMNS) have been measured. The effects of various parameters such as surfactant concentration, salinity and sodium carbonate concentration on the interfacial behavior of crude oil-water were investigated. It was found that the prepared surfactants can reduce the interfacial tension to ultra-low only at certain surfactant concentration, salinity and alkaline concentration ranges. It was also found that there exist optimum values with respect to all of surfactant concentration, salinity and alkaline concentration. The DIT can low to 10(-6) mN.m(-1) under the optimum conditions. Moreover, the DIT behavior of OMNS flooding without alkaline has also been investigated. It was found that the DIT also reaches ultra-low value under the optimum sodium chloride concentration without alkaline. The results show that the OMNS is more effective on lowering surface tension of aqueous solutions and dynamic interfacial tensions (DIT) between crude oil and water. OMNS possesses a great potential to be used in EOR with low costs and high efficiency.