The　present　paper　performs　experimental　and　numerical　investigations　on　the　global　performance　and　internal　flow　of　a　supersonic　air　ejector.　The　effects　of　operation　parameters　and　geometrical　factor　on　the　air　ejector　performance　have　been　analyzed.　The　results　show　that:　the　static　wall　pressure　and　axisymmetric　line　static　pressure　remain　constant　in　critical　mode　under　different　discharged　pressures,　but　they　both　increase　in　sub-critical　mode　with　the　increase　of　the　discharged　pressure.　The　shock　position　of　the　mixed　fluid　moves　upstream　in　critical　mode.　The　second　shock　position　disappears　in　sub-critical　mode.　The　experimental　and　numerical　results　indicate　that　there　exists　an　optimal　nozzle　exit　position　(NXP)　corresponding　to　maximum　entrainment　ratio,　but　the　critical　value　of　discharged　pressure　is　almost　independent　of　NXP.　(C)　2014　Elsevier　Ltd.　All　rights　reserved.