The invention relates to the field of metal material corrosion detection, and in particular relates to an outer box body for a simulative corrosion test of an upper deck of a cargo oil tank, and a using method of the outer box body. The outer box body comprises a box body (11) and an upper cover (3), wherein the upper cover (3) is connected with a support block (6) by an upper cover oil cylinder (5), and the support block (6) is fixed at the outer side of the bottom of the box body (11); thermoelectric refrigeration pieces are respectively arranged on the side walls (15) of the box body (11); the bottom of the box body (11) is provided with a temperature control probe (12); the outer wall of the box body (11) is provided with a double-crystal temperature control box; the thermoelectric refrigeration pieces and the temperature control probe (12) are electrically connected with the double-crystal temperature control box; the double-crystal temperature control box is connected with a personal computer (PC) by data; the bottom of the box body (11) is provided with a support plate oil cylinder (8); a driving end of the support plate oil cylinder (8) is connected with a support plate (9) by a supporting plate (10); the upper part of the support plate (9) is provided with a support plate clamping groove (14) used for bearing a reaction kettle. The outer box body is simple in structure, convenient to use, free from noise and controllable in heating and refrigerating; after the outer box body is used, the experimental environment simulated by the reaction kettle is closer to the real condition.