Chemical sensors based on ZnO nanostructure were fabricated and studied toward ethanol vapour. The adding metal by metal impregnation technique was used for sensitivity improvement of ethanol sensor based on ZnO nanostructure. ZnO nanostructures were prepared by thermal oxidation technique under normal atmosphere and exhibited diameter of 40-300 nm and length of several micrometers. The ethanol sensing properties of sensor based on ZnO nanostructure with platinum and gold nanoparticle were investigated. The improvement of sensitivity due to metal adding was observed and found that adding metal with both Au and Pt resulted in the highest sensitivity of 85 at 1000 ppm. The sensitivity improvement by metal impregnation is due to catalytic properties of metal in both ethanol adsorption reaction KEth(T) and oxygen adsorption reaction KOxy(T) at the surface as described in sensitivity formula. Copyright © 2011 American Scientific Publishers All rights reserved.