CuO-CeO2 Nanocomposites were prepared by hydrothermal synthesis using Ce(NO3)3?6H2O and Cu(NO3)2?3H2O as raw materials and NaOH as precipitant. The materials were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope(TEM), Uv-visible absorption spectrum (UV-vis), X-ray photoelectron spectroscopy(XPS) and specific surface and aperture distribution measurement technique. The researches shows that compared with pure CeO2, CuO-CeO2 has a smaller particle size of 10~40 nm, and a larger specific surface area 38 m2/g. CuO-CeO2 has a good gas-sensitive response to acetone, and its sensitivity to 100 mg/L acetone is 95, which is 43 times higher than that of pure CeO2. The mechanism of enhancing gas sensing properties was discussed in detail, which is attributed to the increase of specific surface area of CuO and CeO2 compound and the formation of p-n heterojunction at the interface between CuO and CeO2.