The　action　of　bus　pulling　in　and　out　of　bus　stop　on　urban　expressway　has　a　spread　effect　on　the　main　road　traffic　flow,　which　leads　to　the　queue　or　traffic　congestion　on　the　main　road　during　rush　hours.　By　taking　a　section　in　the　South　Third　Ring　Road　of　Beijing　as　example,　the　traffic　flow　parameters　of　wave　source　in　the　upstream　and　downstream　were　investigated　and　analysed,　and　the　parameters　describing　the　fluctuation　characteristics　were　obtained.　The　traffic　fluctuation　rules　were　also　studied　by　spatial-temporal　scales.　By　monitoring　the　abnormal　changes　in　traffic　fluctuations,　a　rapid　responsive　strategy　can　be　given　by　the　traffic　management　departments　according　to　different　types　and　levels　of　traffic　disturbances,　which　can　provide　technology　sustains　and　ensure　the　traffic　safety.　(C)　2016　Published　by　Elsevier　Ltd.