Abstract: The dehydrogenation cracking of i-butane was studied over mixed catalysts comprised of Cr2O3/Al2O3 dehydrogenation catalyst and HZSM-5 catalyst in a fixed-bed reactor. The results demonstrate that conversion and product distribution vary signi?cantly depending on different location of Cr2O3/Al2O3 and HZSM-5 catalyst and the amount of Cr2O3/Al2O3 catalyst in the reactor, and the reaction performance is the best when two kinds of catalysts are homogeneously mixed. On the mixed catalyst HZSM-5 with a 20% Cr2O3/Al2O3, the conversion of reaction is 81%, and the yield of ethylene, propylene and butylene is 12.4%, 24.1% and 13.4%, respectively. The conversion increases by 21% and the selectivity of total olefins (ethylene, propylene and butylene) increases by 2.57%, compared with the pure HZSM-5. Besides, i-butane mixed with N2 enters the reactor at a fixed residence time of i-butane, the reaction results become better, and the advantage are more obvious as dilution ratio increases.