The adsorption, tautomerization, and hydrogenation of acetone on Pt(111) surfaces were investigated by using density function theory calculations. The role of the keto enol isomerization on selective hydrogenation and unselective decomposition of acetone was also studied. The results revealed that only a small amount of the adsorbed acetone could undergo enolization and subsequently decompose on clean Pt(111) surface at moderate condition. The enol tautomer is the origin of acetone decomposition on Pt(111) surface. The effect of the keto enol isomerization on hydrogenation of acetone on Pt(111) under sufficient hydrogen pressure is not significant. These results suggested that the keto enol isomerization could not enhance the selective hydrogenation of acetone on Pt(111) surface.