The present invention relates to a catalyst having improved selectivity and reactivity and applied to preparing olefins by dehydrogenating C9 to C13 paraffin, and particularly to a technique for preparing a catalyst, which uses a heat-treated support having controlled pores, and most of metal components contained therein are distributed evenly in a support in the form of an alloy rather than in the form of each separate metal, thereby exhibiting high a conversion rate and selectivity when used in dehydrogenation.