Dehydrogenation of propane to propylene in carbon dioxide was investigated over promoted Cr/SiO2. The results showed that the catalysts were effective for the reaction and CO2 in the feed promoted the catalytic activity. XRD, TPR and microcalorimetric adsorption techniques were used to study the structure and surface acidity of the catalysts. It was found that the surface acidity decreased with the increase of K in the Cr/SiO2 and led to the increase of selectivity toward propylene. A propane conversion of 31% with 91% selectivity to propylene over the 5%Cr-0.4%K/SiO2 catalyst was observed at 923 K with CO2/C3H8 molar ratio of 3.6.