The　effect　of　support　pre-fluorination　on　the　physical　properties　and　catalytic　activity　of　MoCo/　Al2O3-TiO2　was　studied　by　XRD,　N-2　adsorption,　and　thiophene　hydrodesulfurization　(HDS).　Freon　(CFC-12).　in　wet　air　or　in　NH4F　solution　was　used　as　fluorinating　reagents.　The　influence　of　CFC-12　content,　effect　of　fluorination　temperature　and　fluorinating　time　on　the　structure　and　hydrodesulfurization　activity　of　the　catalysts　were　examined　systematically.　The　results　revealed　that　hydrodesulfurization　activity　of　the　catalyst　fluorinated　by　1%　CFC-12　at　623　K　was　obviously　improved　with　an　increase　of　20%　similar　to　30%　as　compared　with　that　of　the　unfluorinated　catalyst,　the　commercially　available　BY2　catalyst,　and　NH4F-fluorinated　catalysts.　Moreover,　the　catalyst　fluorinated　by　the　Freon　gas　presented　excellent　stability　on　catalytic　activity　and　structure.