In-situ DRIFTS was used to study the deep oxidation of propane,a side reaction during propane oxidative dehydrogenation to propene. Strong adsorption of propene was supposed to be the main reason for the deep oxidation. It was found that gaseous oxygen in the feed and the reaction temperature had great influence on the reaction. To obtain a relative high selectivity to propene,the reaction temperature should be maintained at 150～250 ℃ with a proper content of gaseous oxygen in the feed for a certain catalyst and some modifiers which could weaken the adsorption of pmpene on the catalyst surface would be favorable.