Nanometer ZnO-base composite oxides were prepared by the inorganic salt sol-gel(ISG) method, and their structures were studied using XRD. The gas sensors were prepared from the nanometer ZnO-base composite oxides, and their sensing properties to different concentration of C2H5OH gases were investigated. A composition of Al/ZnO=1.5 mol% sensor shows a maximum sensitivity of 26 to 2 000 g/g C2H5OH. The composite oxide Sb/Al/ZnO=5?3?100(mol)% has good gas sensing properties over wider working temperature range. The physical and chemical adsorptions and the gas-sensing mechanism of the composite oxide Sb/Al/ZnO were discussed.