The amphiphilic dodecylbenzenesulfonic acid (DBSA) is usually added into wells as an asphaltene precipitation inhibitor. The interfacially active DBSA and asphaltenes will be both adsorbed at the oil-water interface, influencing the stability of crude oil emulsions. The interactive effects between DBSA and asphaltenes on the stability and interfacial properties are investigated in this paper. First, the emulsions containing DBSA and asphaltenes are prepared, followed by a bottle test. DBSA weakens the stability of the emulsion and migrates from the oil to the water phase through the interface. Then, the adsorption process of DBSA and asphaltenes is investigated by measuring the dynamic interfacial tension. DBSA and asphaltenes are found to form a composite interfacial layer with a competitive adsorption mechanism. The viscoelasticity of the layer is explored by measuring the dilational modulus. The modulus declines after adding DBSA, proving that the strength of the layer is decreased. Meanwhile, the compressibility of the layer is proved to be stronger by adding DBSA based on the crumpling ratio measurement. A series of experiments are carried out to explore the dispersive state of asphaltenes influenced by DBSA. DBSA and asphaltenes are supposed to form composite particles. The alkyl chain of the composite particles stretches in the bulk phase, giving them good oil compatibility. Therefore, the dispersive state of asphaltenes is improved by DBSA.