A platinum-substituted alumina-promoted sulfated zirconia (PtAu/SZA) was prepared and used for the conversion of isobutane to n-butane, aiming to optimize the ethylene feedstock in the steam thermal cracking process and increase the ethylene yield. PtAu bimetallic catalysts showed higher catalytic activity than Pt-alone catalyst, and the enhancement is attributed to PtAu alloying. By diluting and separating Pt with PtAu alloy agglomerates, continuous Pt agglomerates disappear and hydrogen dissociation on Pt is enhanced. In addition, the reduction temperature of Pt is decreased with the increase in Au content, while the reduction temperature of sulfate was increased which will delay the loss of sulfate according to the results of H2-TPR and NH3-TPD. However, the acidity of the catalyst decreases with the increase in Au, which is due to that PtAu alloy covers the acid sites on the surface. Overall, we found that the Pt0.5Au0.3/SZA showed the highest yield to n-butane (34.69%).