In　this　paper,　an　attempt　was　made　to　obtain　the　aerodynamic　performance　of　a　Hex-rotor　unmanned　aerial　vehicle　with　different　rotor　spacing.　The　hover　efficiency　of　the　Hex-rotor　unmanned　aerial　vehicle　is　analyzed　by　both　experimental　tests　and　numerical　simulations.　First,　a　series　of　index　to　characterize　the　aerodynamic　performance　of　the　Hex-rotor　unmanned　aerial　vehicle　are　analyzed　theoretically,　and　then　both　tests　and　simulations　on　a　Hex-rotor　unmanned　aerial　vehicle　with　different　rotor　spacing　ratio　(i　=　0.50,　0.56,　0.63,　0.71,　0.83)　were　presented　in　details.　For　a　custom-designed　test　platform,　the　thrust,　power　loading　and　hover　efficiency　of　the　Hex-rotor　unmanned　aerial　vehicle　were　obtained　in　this　paper.　Finally,　computational　fluid　dynamics　simulations　are　performed　to　obtain　the　streamline　distributions　of　the　flow　field,　pressure　and　velocity　contour　of　the　Hex-rotor　unmanned　aerial　vehicle.　Results　show　that　the　aerodynamic　performance　of　the　Hex-rotor　unmanned　aerial　vehicle　is　varied　by　changing　the　rotor　spacing.　Specifically,　the　smaller　rotor　spacing　may　improve　the　aerodynamic　performance　of　the　Hex-rotor　unmanned　aerial　vehicle　by　increasing　the　rotor　interferences.　In　the　meantime,　the　effects　of　mutual　interference　between　the　rotors　are　gradually　reduced　with　the　increase　of　the　rotor　spacing.　Moreover,　the　uniformity　of　the　streamline　distribution,　the　shape　and　the　symmetry　of　the　vortex　are　necessary　conditions　for　the　Hex-rotor　unmanned　aerial　vehicle　to　generate　a　larger　thrust.　It　was　also　noted　that　the　thrust　increased　by　5.61%　and　the　overall　efficiency　increased　by　about　8.37%　at　i　=　0.63　for　the　working　mode　(2200　r/min),　which　indicated　that　the　rotor　spacing　ratio　at　i　=　0.63　obtained　a　best　aerodynamic　performance.　©　The　Author(s)　2020.