Abstract: Graphene oxide films were prepared by the modified Hummers method, which includes sonication, aggregation and self-assembly. The graphene films were obtained by vacuum heat treatment of the graphene oxide films. XRD, SEM, FTIR and Raman spectroscopy were used to investigate the microstructure evolution of the films during preparation. It is found that self-assembly is a simple method to produce graphene oxide films with controllable size and perfect stacks of graphene oxide layers. Heat treatment gives the graphene films high electrical conductivities. The electrical conductivity of the films increases up to 536S/cm with increasing heat treatment temperature under vacuum.