By adding an EO-PO demulsifier, the interface between the asphaltene model compounds and water was changed. The adsorption replacement of CSPe or CSPeC11 molecules by an EO-PO demulsifier and the competitive adsorption between them were compared. A reduction of the interfacial tension of the CSPe or C5PeC11-water interface by EO-PO demulsifier addition for the water-in-oil (W/O) and oil-in-water (O/W) systems was observed, suggesting higher interfacial activities of the EO-PO demulsifier, especially at high EO-PO demulsifier concentrations. Crumpling ratios of the flat CSPe-water interfacial film for W/O and O/W systems were also measured, and the results showed that the EO-PO demulsifier was capable of softening and weakening the interfacial films for both systems. The EO-PO demulsifier showed similar performance on changing the CSPe interfacial film through both diffusion (simulating the W/O system) and spreading (simulating the O/W system) protocols. By investigating the Langmuir interfacial-area isotherms, it was found that the CSPe-water interfacial film became much more compressible with the addition of the EO-PO demulsifier. The EO-PO demulsifier could also destroy the integrity of the CSPe interfacial film or avoid a networked film formation as indicated by atomic force microscopy images. In addition, shear rheology measurements showed that the rigidity of the CSPe interfacial film was dramatically reduced or even absent in the presence of the EO-PO demulsifier. Moreover, the changes in the CSPe-water interface by the EO-PO demulsifier were similar to those of the EO-PO/asphaltene system, providing further justification for using CSPe as the asphaltene model compound.