Graphene oxide (GO) has gathered widespread interest within the scientific community as a result of its unique properties. In the present work, the interfacial behavior of the GO nanosheet at the crude oil/water interface was explored to investigate its demulsification mechanism for crude oil/water emulsions. The interfacial rheology properties and the interfacial tension were systematically discussed. The results revealed that GO was able to decrease the interfacial tension of the emulsion to a large extent, implying that the GO nanosheet was interfacially active. Unexpectedly, the dilational modulus monotonically increased with increasing the GO dosage. In addition, the coalescence kinetics and the interfacial assembly behaviors of GO were investigated. It was observed that the oil droplet became wrinkled once contacting with the crude oil/water interface, and a thin film was finally left at the interface. Therefore, the GO nanosheet was thought to be able to diffuse to the oil/water interface and self -assembled to jam into a new solid thin "GO film", leading to the increase of the determined dilational modulus of the interface. The morphology of the film was revealed by a confocal fluorescence microscope, and a wrinkled and continuous morphology was observed, implying that the GO nanosheet aligned parallel to the oil/water interface. The findings in the present study are crucial for fully understanding the demulsification mechanism of GO and might provide a facile way to prepare large area GO thin films.