The invention relates to the technical field of mine ore grinding machinery and discloses a disassembling and assembling device used for an extra large-sized (semi) autogenous mill feeding sealing ring. The disassembling and assembling device comprises a disassembling and assembling bracket and hydraulic jacking mechanisms. The disassembling and assembling bracket comprises a base, a pallet fork insertion groove fixed to the bottom of the base, a pulley bracket fixed to the top of the base and a fixed pulley. Each hydraulic jacking mechanism comprises a fixed frame and a hydraulic cylinder. The fixed frames are fixedly connected with an installation flange of the sealing ring. Cylinder bodies of the hydraulic cylinders are fixedly connected with the fixed frames. Telescopic rods correspond to first bolt holes, corresponding to the fixed frames, in the sealing ring installation flange. The multiple hydraulic jacking mechanisms are arranged on the installation flange of the sealing ring at intervals. According to the disassembling and assembling device used for the extra large-sized (semi) autogenous mill feeding sealing ring, the mechanisms are fully used to replace workers to conduct the work of close-distance operation, and the safety of carrying out the work is greatly improved; and by means of the reasonably-designed tool, the heavy and difficult work of disassembling and assembling the feeding sealing ring becomes savable in time and effort, thus, the working efficiency is improved, and the machine halt time is shortened.