Abstract: The interfacial dilational viscoelastic properties of hydrophobically associating block copolymer composed of acrylamide (AM) and a low amount of 2-ethylhexyl acrylate (EHA) (＜ 1.0% mole fraction) with a hydrolysis degree of about 1.5%～2.0% at the octane-water interfaces were investigated by interfacial tension relaxation method. The influences of anionic surfactant sodium dodecyl sulfate (SDS), cationic surfactant cetyl trimethylammonium bromide (CTAB) and nonionic surfactant Triton X-100 on the dilational viscoelastic properties of 7 g•L-1 polymer solutions were studied. The results showed that surfactants can influence the dilational properties of polymer solutions by providing a new fast relaxation process involving the exchange of surfactant molecules between monomers and mixed micelles at interface. By adding SDS, this new process is so fast that its characteristic time can′t be obtained. However, for Triton X-100, which has a relative higher molecular weight, the characteristic time was about 0.9 s. By adding CTAB, the slow process changed obviously due to the strong electrostatic interaction between oppositely charged surfactant and hydrolyzed part of polymer chain.