Abstract: Graphite oxide was synthesized by the Hummers and Offemann method, followed by ultrasonic delamination in water to produce a stable hydrosol of graphene oxide sheets. The graphene oxide films were prepared from the hydrosol by a vacuum-assisted self-assembly technique. These films were further treated in a vacuum oven at different temperatures, and characterized by Fourier transform infrared spectroscopy, X-ray diffraction, Raman spectroscopy, and scanning and transmission electron microscopy. Results indicate that the graphene oxide films exhibit good electrical conductivity up to 527S/m after the thermal treatment at temperatures from 130 to 200℃. This environmentally friendly and easy approach is promising for the large scale preparation of graphene oxide films with no need of hydrazine and other toxic chemicals.