At　present,　researches　on　the　adaptive　reclosure　lack　an　analytic　expression　for　beat　frequency　current　about　whether　the　beat　frequency　current　definitely　exists　and　the　range　of　amplitude　of　the　current　in　adaptive　reclosure.　The　amplitude　may　be　nonexistent　or　too　small　when　the　single-phase　transient　fault　disappears,　which　will　affect　the　reliability　of　reclosing　determination.　The　beat　frequency　current　in　the　shunt　reactor　is　not　only　affected　by　sound　phase　voltage　but　also　by　the　initial　state　of　components　of　transmission　line　when　fault　disappears.　Based　on　the　superposition　principle,　the　complete　expression　of　beat　frequency　current　is　obtained,　by　an　analysis　of　which　the　minimum　beat　frequency　current　and　conditions　for　its　occurrence　are　obtained.　It　is　concluded　that　the　beat　frequency　current　being　zero　belongs　to　small　probability　event.　The　current　is　affected　by　fault　time,　arc　duration,　arc　resistance,　phase　angle　difference　and　fault　location　that　make　the　amplitude　obvious.　If　the　amplitude　is　too　small,　it　will　affect　the　reliability　of　the　reclosing　determination.　The　paper　gives　the　range　of　amplitude　of　the　beat　frequency　current　on　500　kV　transmission　lines　using　the　method　of　the　orthogonal　experiment　in　mathematical　statistics,　proving　the　beat　frequency　current　can　be　applied　to　engineering.　©,　2015,　Automation　of　Electric　Power　Systems　Press.　All　right　reserved.