The invention provides an unmanned aerial vehicle multi-battery pack charging circuit automatic switching device and method. The device is applied to an unmanned aerial vehicle, a power circuit, a load circuit and a charging circuit are arranged in the unmanned aerial vehicle, the unmanned aerial vehicle multi-battery pack charging circuit automatic switching device comprises an automatic circuit-changing device and a charging controller, wherein the charging controller is connected with the automatic circuit-changing device and is used for controlling the automatic circuit-changing device; and the automatic circuit-changing device is used for disconnecting the power circuit from the load circuit and therefore connecting the power circuit with the charging circuit for charging battery packs of an unmanned aerial vehicle power supply, or the automatic circuit-changing device is used for disconnecting the power circuit from the charging circuit, and therefore connecting the power circuitwith the load circuit for enabling the unmanned aerial vehicle power supply to electrify the unmanned aerial vehicle. The load circuit and the charging circuit in the unmanned aerial vehicle are automatically switched, the power line communicates with the charging circuit, and the battery packs of the unmanned aerial vehicle power supply can be charged without being taken out.