Abstract: The dilational viscoelasticity of the interfacial film formed by interfacial active components of crude oil at n-decane/water interface was investigated.The interfacial active components was obtained by supercritical fluid extraction and fractionation(SFEF) method from Iranian heavy oil.The properties of the two samples that have different average molecular weights and the influence of temperature on these properties were studied.The results show that the sample of higher average molecular weight has higher dynamic interfacial dilational activity.From the slope of the lg|ε|～lgω curve and the result of phase angle we can infer that the primary relaxation mechanism is not of diffusion-control but perhaps of adsorption-barrier-control.Temperature profoundly influences the dilational viscoelasticity of interfacial films of the two samples.Increasing temperature decreases the amplitude of dilational modulus and viscosity of the film,and alter the frequency response of phase angle of dilational modulus.