With a simple coarse-grained model, the properties of sodium dodecylbenzene sulphonate (SDBS) adsorbed at the water/oil interface, has been investigated on a mesoscopic level by considering the variation of interfacial density using dissipative particle dynamics (DPD) simulation. Compared with sodium dodecyl sulphonate systems, sodium dodecylbenzene sulphonate are more efficient. An increase of surfactants interfacial concentration results in the increase of its interfacial density before reaching a full monolayer and appropriate salts make surfactant molecules adsorbed more at interface. It is beneficial to decrease interfacial tension if the hydrophobic chains of the surfactant and the oil have similar structure. The simulation conclusions are well consistent with the experimental results. Also with computer simulation method, we have observed that SDBS is not distributed homogeneously over the interface. Rather, the interfacial layer contains large cavities between SDBS clusters filled with water or oil clusters. When TX-100 molecules were introduced, clusters formed by nonionic surfactants filled SDBS cavities, thus decreased the interfacial tension to ultra low, even lower than 10^－3 mN•m^－1. This inhomogeneous distribution helps to enhance our understanding of the synergism interaction of the different surfactants.

Key words: dissipative particle dynamics, interfacial density, interfacial efficiency, salt alkylbenzene sulphonate