COVID-19　has　threatened　human　lives.　Countries　have　implemented　various　interventions　such　as　vaccination,　mask-wearing,　body　temperature　screening,　and　isolation.　However,　the　effectiveness　of　single　and　combined　interventions　has　not　yet　been　accurately　analyzed.　In　this　study,　an　improved　SEIR　model　considering　both　real　human　indoor　close　contact　behaviors　and　susceptibility　to　COVID-19　was　established.　Taking　Hong　Kong　as　an　example,　a　quantitative　assessment　of　the　relationship　between　the　efficiency　of　single　and　combined　interventions　and　implementation　time　and　intensity　was　carried　out.　The　results　showed　that　the　infection　risk　(one-hour　close　contact　with　an　infected　person)　of　COVID-19　of　students,　workers,　and　non-workers/non-students　was　3.1%,　8.7%,　and　13.6%,　respectively.　Workplace　closures　were　more　effective　among　built　environment　interventions.　If　mask-wearing　was　mandatorily　required　in　schools,　workplaces,　supermarkets,　shopping　centers,　and　public　transport,　COVID-19　could　not　be　totally　restricted.　Workers　should　be　prioritized　for　vaccination,　followed　by　non-workers/non-students　and　students.　Among　all　interventions,　reducing　close　contact　rate　and　increasing　vaccination　rate　were　better　interventions.　There　was　no　COVID-19　outbreak　(basic　reproduction　number　R-0　=　1)　if　the　close　contact　reduction　rate　was　59.9%　or　the　vaccination　rate　reached　89.5%.　The　results　may　provide　scientific　support　for　COVID-19　prevention　and　control.