After craniotomy, the skull needs to be reset. In the past, craniotomy was done with a wire saw, and when sawing the skull, a beveled surface could be made at the edge of the skull, so that the free bone fragments could be placed directly on top of the bone window after the operation, and the beveled surface would not cause the bone fragments to collapse. Now we use a milling cutter to open the skull, after milling, a crack will be formed between the free bone piece and the normal skull, the bone piece can not be placed directly on the bone window can be connected with a titanium plate, one end of the titanium plate is placed on the edge of the bone window, the other end is placed on top of the free bone piece, and the titanium screws are used for fixation, and an appropriate number of titanium screws and titanium plates will be selected according to the size of the bone window to fix the skull.