The Cr/Al2O3 catalyst is a typical commercial catalyst system that has been widely applied for propane dehydrogenation (PDH). Appreciable improvement in catalytic performance of this catalyst is of importance regarding its further applications, but investigations of the interaction between Ce and Cr species and the effects of Ce modification on the dispersion and distribution of the active Cr phases have seldom been concerned in the previous works. In this work, M/Al2O3 (M: Cr, Ce, and Ce-Cr) catalysts were synthesized and the Ce-modified catalyst exhibited enhanced activity. It was shown that modification of Ce on the Cr/Al2O3 catalyst decreased the amount of inactive isolated Cr(VI) sites. Meanwhile, the increased amount of oxygen vacancy was observed over the Ce Cr/Al2O3 catalyst, which promoted the interaction between Ce and Cr species. The above results can be confirmed by the characterization results of X-ray diffraction, UV vis, H-2-temperature-programmed reduction, X-ray photoelectron spectroscopy, and Raman spectroscopy, which provide meaningful information for improving catalytic performance of the commercial Cr/Al2O3 catalyst during PDH.