Some　analyses　on　air-air　ejector　are　presented,　which　focus　on　the　effects　of　fluid　state　parameters　on　the　ejection　coefficient　by　numerical　calculation.　Results　indicate　that　to　increase　the　pressure　of　working　fluid　or　infection　fluid　is　effective　to　obtain　a　high　ejection　coefficient　of　air-air　ejector,　and　so　it　is　to　decrease　the　pressure　of　mixing　fluid.　Besides,　increase　the　temperature　of　working　fluid　or　decrease　the　temperature　of　infection　fluid　is　also　helpful　to　get　a　high　ejection　coefficient.　©　2011　IEEE.