The invention discloses a load plate model test device and a load plate model test method capable of reusing and applying preloading. The device comprises the following parts: a plurality of reactionframes in a square frame structure, wherein the plurality of reaction frames are arranged vertically and parallel to each other, and are connected to an integrated structure by the I-beams along bothsides of the lower end of the length direction; a model box, which is in a square structure with an open upper surface, wherein the model box is filled with test soil material, the opening on the upper surface is matched with a horizontal pre-stressed steel plate, the model box is located between the plurality of reaction frames, and both sides of the model box in the width direction protrude outfrom both sides of the reaction frames in width direction; and a plurality of jacks, of which the upper ends stand up to the reaction frames, and the lower ends are evenly distributed on the pre-compressed steel plate. The method applies a preloading through the device. The device and method can make the test repeatedly used and partially repaired while satisfying the preloading condition, which can avoid a large amount of waste of materials, and create great economic benefits.