Novel chemo-resistive gas sensors based on reduced graphite oxide (rGO) thin films have been fabricated and evaluated for hydrogen detection. The rGO materials were thermally treated at various conditions and analyzed using X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy techniques to investigate the change of functional groups. The semiconductor type of the rGOs treated at different conditions were checked by flowing hydrogen gas at 20cm3/min (sccm) under 10Torr partial pressure. The rGOs treated at 70°C in atmosphere (rGO070a), 200°C in a vacuum (rGO200v), and 500°C in a vacuum (rGO500v) exhibited n-type, ambipolar, and p-type behavior, respectively. The rGO500v was adopted as active sensing element without any rare metal decoration, and its sensing response to hydrogen was studied by using air as carrier gas. The rGO500v exhibited good sensitivity (∼4.5%), response time (∼20s), and recovery time (∼10s) to 160ppm hydrogen gas at room temperature.