Carbon thin films were prepared by hot filament assisted sputtering system. The sputtering gas was pure Ar (99.9995%), and the temperature of the filament was 2000degreesC. The properties of the carbon thin films were investigated by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Nano fibers were observed in the carbon films by SEM and TEM measurement. No catalytic material was detected in the fiber. The diameter was about 10 nm.