The　effect　of　area　ratio,　Coanda　surface　curvature,　inlet　condition　and　pressure　coefficient　on　the　ejection　coefficient　of　the　Coanda　annular　jet　element　is　studied　in　this　paper.　The　results　of　the　study　show　that:　A　linear　relationship　between　the　ejection　coefficient　and　the　area　ratio　of　the　Coanda　annular　jet　element;　For　a　Coanda　annular　jet　element　with　certain　structure,　the　inlet　conditions　have　little　effect　on　the　ejection　coefficient;　Increasing　the　Coanda　surface　curvature　in　a　certain　range　can　increase　the　ejection　coefficient　of　the　Coanda　annular　jet　element;　The　mechanism　of　increasing　ejection　coefficient　of　Coanda　annular　jet　element　by　Coanda　effect　is　revealed;　The　increase　of　the　pressure　coefficient　makes　the　coefficient　of　the　internal　reflux　of　the　Coanda　annular　jet　element　reduced.　©　2018,　Science　Press.　All　right　reserved.