The selectivity and reactivity in the hydrogenation of 1,3-butadiene catalyzed by T-1-modified 5 wt% Pd/Al2O3 catalysts vary with amounts of T1 loading and with the reduction temperatures, that is, the main product was l-butene and trans-2-butene for values of T1 loading of 0.5 and 2 in T1/Pd atomic ratio, respectively, when the catalysts were reduced at 673 K. 1,3-butadiene was hydrogenated selectively towards l-butene and trans-2-butene when the T1 modified 5 wt% Pd/Al2O3 catalyst of T1/Pd = 2 was reduced at 300 and 373 K or above, respectively. On the catalyst with T1/Pd 2 reduced at 373 K or above, the butenes formed are not hydrogenated to butane, even after a long reaction time. These results suggest the formation of Pd-T1 alloy or intermetallic compounds during the reduction procedure which is responsible for the selectivity controlling in the reaction. TPR and XRD results were in consistence with the reaction data.