This　paper　investigates　the　aerodynamic　performance　of　an　overlapping　octocopter　with　the　effect　of　horizontal　wind　ranging　from　0　to　4　m/s　using　both　low-speed　wind　tunnel　tests　and　numerical　simulations.　The　hovering　efficiency　and　the　potential　control　strategies　of　the　octocopter　under　the　effect　of　horizontal　wind　are　also　validated　using　blade　element　momentum　theory.　The　velocity　distribution,　rotor　pressure　and　vortex　of　the　downwash　flow　with　the　horizontal　wind　are　presented　using　the　Computational　Fluid　Dynamics　(CFD)　method.　Finally,　wind　tunnel　tests　were　performed　to　obtain　the　thrust　and　power　consumption　with　the　rotor　speed　ranging　from　1500　to　2200　rpm　for　horizontal　winds　at　0　m/s,　2.5　m/s　and　4　m/s.　The　results　showed　that　horizontal　wind　decreased　the　flight　efficiency　of　the　planar　octocopter　and　had　little　effect　on　the　coaxial　octocopter.　It　is　also　interesting　to　note　that　horizontal　wind　is　beneficial　for　thrust　increments　at　a　higher　rotor　speed　and　power　decrements　at　a　lower　rotor　speed　for　the　overlapping　octocopter.　Specifically,　the　horizontal　wind　of　2.5　m/s　for　a　lower　rpm　is　presented　with　a　power　decrement　with　proper　aerodynamic　interference　between　the　rotor　blades.　Additionally,　the　overlapping　octocopter　obtains　a　higher　hover　efficiency　at　4　m/s　compared　to　traditional　octocopters,　which　is　more　suitable　for　flying　in　a　cross　wind　with　a　more　compact　structure.