The invention relates to a method for preparing a positive electrode material of an alloy-reinforced anoxic stannic oxide nanosheet array supercapacitor, and belongs to the technical field of preparation of new energy materials and its application. The positive electrode material is composed of an anoxic stannic oxide nanosheet array grown on a foamed nickel substrate and partially Sn-Ni alloyed.The nanosheets grow so as to be vertically staggered to form a wall shape. As an operating electrode, the positive electrode material has a large specific capacitance, good cycle stability, and no harm to the human body. The method comprises firstly using stannous chloride dihydrate and trisodium citrate dihydrate as raw materials, and growing the raw materials by a solvothermal method on a foamednickel substrate to obtain an anoxic stannic oxide wall-shaped nanosheet array structure; and performing high-temperature thermal reduction and alloying in a vacuum tubular furnace to finally obtainthe positive electrode material. The method has large product output, achieves controllable compositions and shapes, uses simple raw materials, equipment and technological processes, and is low in cost, safe, clean and environment-friendly in production process, and beneficial to large-scale production.