A facile one-step hydrothermal method for a novel discoid crystal of rutile SnO₂modified by reduced graphene oxide (rGO) is reported in this work. X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) were performed to characterize the structure and morphology of the SnO₂/rGO composites. Uniform discoid rutile SnO₂monocrystal with a diameter of approximately 100 nm and a center thickness of 40 nm was anchored on both sides of rGO nanosheets. The SnO₂/rGO composite exhibited preferential detection toward NO₂with high response, good selectivity and reproducibility. The response of the sensor to 1 ppm NO₂at 75℃was nearly one order of magnitude higher than that of SnO₂, and the detection limit was improved to 50 ppb. The improved response was discussed and the gas sensing mechanism was established.