Emergencies　on　urban　rail　transit　(URT)　rely　on　understanding　passenger　flow.　It　is　necessary　to　study　the　characteristics　of　passenger　flow　and　determine　the　scope　of　the　emergency　in　a　timely　and　reasonable　fashion.　This　paper　uses　an　impact　analysis　method　of　passenger　volume　under　emergent　condition　of　URT　using　automated　fare　collection　(AFC)　data.　Based　on　the　method,　the　affected　scope　is　determined,　and　the　analysis　methods　of　the　characteristics　of　passenger　flow　within　emergent　impact　scope　can　be　proposed.　Lastly,　combining　with　AFC　data　of　Beijing　URT,　this　paper　analyzes　spatial　and　temporal　distribution　characteristics,　change　characteristics　of　passenger　volume　at　key　stations　and　the　number　of　stations　affected　by　the　emergent　event,　and　summarizes　passenger　flow　change　rule　under　emergent　condition.　This　quantitative　analysis　method　has　universal　applicability　in　providing　support　for　distribution　of　passenger　flow,　predicting　passenger　flow,　and　early　warning　of　URT　emergency.　©　ASCE.