The　flow　rate　of　the　extraction　system　and　velocity　field　on　the　platform　of　a　typical　monolayer　island　station　of　Line　1　and　Line　2　of　the　Beijing　Metro　were　measured　in　December　2005.　Based　on　the　measured　values,　numerical　analysis　was　made　to　evaluate　the　current　flow　states　in　the　station.　Moreover,　the　smoke　velocity,　temperature　and　concentration　distribution　in　case　of　station　fire　under　different　extraction　modes　were　analyzed,　then　the　optimal　smoke　extraction　mode　was　proposed.　Reference　was　offered　for　the　running　modes　of　the　existing　subway　extraction　system　and　the　design　of　the　future　subway　extraction　system.