Alumina supported Pt, Sn and PtSn catalysts were prepared by impregnation and tested in the gas phase hydrogenation of acetic acid, and characterized by N-2-physisorption, XRD, H-2-TPR, H-2-pulse chemisorption, H2TPD, DRIFTS (diffuse reflectance infrared Fourier transform spectroscopy), XPS, electron microscopy techniques (TEM, HRTEM and EDX). Results show that Sn addition to Pt/Al2O3 catalyst can improve the conversion of acetic acid and suppress the production of by-products, as well as enhance the selectivity towards ethanol. The optimization of activity and selectivity can be achieved by changing reaction temperature and pressure. Characterizations indicated that the better performance of PtSn/Al2O3 catalyst is due to the formation of PtSn alloy and Pt-SnOx species.