The invention relates to a changeable protection box. The size of the protection box itself can be adjusted according to the sizes of goods, so that the changeable protection box is suitable for goods of various specifications, and the changeable protection box has the advantages of being simple in structure, easy to assemble, convenient to transport, good in anti-theft effect and low in cost. According to the technical scheme, the changeable protection box comprises a box body, a box cover and a warning device. The box body is in a rectangle shape and composed of five face plates, and the five face plates comprise the bottom plate, the front plate, the rear plate, the left plate and the right plate, wherein the front plate, the rear plate, the left plate and the right plate perpendicularly intersect with the bottom plate. The left plate and the right plate further perpendicularly intersect with the front plate and the rear plate at the same time, the rear side of the box cover is hinged to the top of the rear plate, and the front plate is provided with a locking device. The changeable protection box is characterized in that the bottom plate, the front plate, the rear plate, the left plate and the right plate respectively comprise at least one rectangular unit splicing plate, and the edge around each unit splicing plate is fixedly connected with one adjacent unit splicing plate in the same face plate through an inserting connection structure or fixedly connected with one adjacent unit splicing plate in one intersecting face plate through an inserting connection structure.