Abstract: Using petroleum intermediate products as original reagents, the hydrocarbon phenyl sulfonate surfactants, named as AS 4,AS 5 and AS 6, have been synthesized. It shows that systems of AS surfactant solution/alkali/crude oil have ultralow interfacial tension of less than 10 -2 mN/m. The influence of isomer compositions, original reagents and the molecular weight of surfactants on AS surfactant interfacial activity are discussed. It shows that to a certain extent effects of original reagents and the change of isomer composition on surfactant interfacial activity are not very striking. The interfacial activity of surfactant will be enhanced when the average molecular weight is increased.