The invention relates to a high-energy-density good-safety energy storage power supply of a large-sized solar unmanned aerial vehicle. The energy storage power supply comprises a battery box body, battery sets arranged in the battery box body, a solar battery charging circuit and battery management system circuit board and an annular seal ring, wherein the battery box body comprises a deformed lower housing and a square upper cover; the annular seal ring is arranged in the inner-side groove of the mounting surface of the lower housing; the deformed shape is an isosceles trapezoid and comprises two straight edges, two isosceles bevel edges and two same transition straight edges; input and output water seal joint mounting seats are arranged on the upper cover; each battery set comprises deformed battery cells, a PCB (printed circuit board) adapter plate, heating plates and a temperature sensor; each heating plate is arranged between the every two adjacent battery cells; each PCB adapter plate is arranged at the top of the battery set, and the tabs of the battery cells are welded on the PCB adapter plates to finish series-parallel connection of the battery sets. The energy storage power supply is high in duty ratio, has waterproof and heating functions, and enables the unmanned aerial vehicle to have all-weather cruising capability.