SnO2 and Au modified SnO2 synthesis method with HAucl4 and SnCI2（acac）2 nanoparticles were prepared by one-pot hydrotherma The morphology, composition and structure of the samples were analyzed by TEM, EDS, XRD and XPS, and the gas sensing performance of the two materials for ethanol was tested. The results show that the morphology of both samples is nanoparticle, and the average diameter is about 9-12 nm. The crystal structure of SnO2 is futile type, and Au is face centered cubic structure. In the sample of Au/SnO2, the mass ratio of Au and SnO2 is 2.6%, and Au element exists with a mixture of Au and Au3＋ valence states. Comparing with pure SnO2 nanoparticles, Au modifing can significantly improve the sensitivity and selectivity of the gas sensors on the response to ethanol.