A　novel　octocopter　with　an　overlapping　rotor　arrangement　is　proposed　in　this　paper　to　increase　the　payload　with　a　limited　size.　The　aerodynamic　performance　was　obtained　by　both　experiments　and　numerical　simulations　with　the　rotor　spacing　ranging　from　1.2　D　to　2.0　D　(L=　1.2　D,　1.4　D,　1.6　D,　1.8　D,　2.0　D).　Also,　the　aerodynamic　parameter　was　evaluated　by　the　thrust,　power　consumption,　thrust　coefficient,　power　coefficient,　and　figure　of　merit　(FM)　in　hover.　Compared　with　a　traditional　co-axial　octocopter,　the　results　indicated　that　the　overlapping　octocopter　at　L=　1.8　D　presented　an　increasing　thrust　up　to　15.98%,　and　the　FM　increment　was　up　to　6%.　Additionally,　the　streamline　distribution　showed　that　the　symmetry　of　the　vortex　movement　in　the　downwash　flow　for　the　overlapping　rotors　will　offset　the　rotor　interference　with　an　increase　in　thrust.　Meanwhile,　the　vortex　deformation　resulting　from　the　induced　velocity　from　the　upper　rotor　also　led　to　an　increase　in　power　consumption.　Finally,　the　optimal　aerodynamic　performance　of　the　overlapping　octocopter　was　obtained　with　a　rotor　spacing　of　L=　1.8　D　at　1800　RPM.