Close　contact　is　considered　as　one　of　the　dominant　routes　of　SARS-CoV-2　transmission,　and　evaluating　people＇s　travel　behavior　is　an　important　way　to　quantify　social　distance.　As　a　main　public　transport,　Mass　Transit　Railway　(MTR)　provides　an　indoor　environment　for　frequent　close　contacts.　Based　on　roughly　4　billion　smartcard　swiping　data　on　subway　in　Hong　Kong　between　January,　2019　and　January,　2021,　the　changes　on　local　travel　behavior　of　different　groups　of　passengers　(adults,　children,　students　and　the　senior　citizens)　due　to　the　pandemic　was　analyzed.　Due　to　the　pandemic,　the　total　number　of　MTR　passengers　decreased　by　an　average　of　41.0%,　and　the　number　of　passengers　on　the　same　carriage　of　adults,　children,　students　and　senior　citizens　during　weekdays　(weekends)　decreased　by　34.5%　(47.8%),　80.0%　(78.3%),　72.9%　(70.3%),　and　30.2%　(42.9%),　respectively.　This　study　provides　scientific　supports　for　strategies　to　deploy　for　COVID-19　prevention　and　control　in　the　subway　system.　©　2023　Healthy　Buildings　2023:　Asia　and　Pacific　Rim.　All　rights　reserved.