The　HZSM-5　zeolites　with　different　mole　ratio　of　SiO　2　/Al　2　O　3　were　characterized　by　in-situ　FT-IR　and　their　n-butane　cracking　activities　were　investigated　in　a　continuous　flow　fixed-bed　micro-reactor　to　reveal　the　relationship　between　Si/Al　ratio,active　sites　and　catalytic　behavior.The　results　indicated　that　the　kind,number,and　strength　of　active　sites　of　HZSM-5　zeolites　with　Si/Al　ratio　of　38　and　200　were　significantly　different.HZSM-5-38　zeolites　have　more　acid　bridging　Si-O(H)-Al　groups　and　non-skeleton　aluminum　hydroxyl　with　strong　acidity,while,HZSM-5-200　zeolites　only　show　several　isolated　hydroxyl　groups　with　small　amount　of　weakly　acidic　or　non-acidic　neighbouring　silica　hydroxyl　groups　in　microporous.HZSM-5-200　zeolites　result　in　higher　yield　of　light　olefins,indicating　that　lower　acid　density　and　strength　is　suitable　for　producing　more　olefins.　©　2019,　Editorial　Office　of　Petroleum　Processing　and　Petrochemicals.　All　right　reserved.