A replacing apparatus for a high-voltage cable GIS terminal large flange is formed by a terminal bushing support device and a split-type large flange. The terminal bushing support device comprises a support small flange top plate (1) which is provided with openings. The bottom surface of the support small flange top plate is provided with fixation nuts (2). Each fixation nut is screwed with a screw rod (3). Each screw rod is provided with an adjustment nut (4). The lower end of each screw rod penetrates through a corresponding through hole in a support leg connection plate (5) and further goes into a corresponding supporting tube (6) fixedly arranged in the bottom surface of the support leg connection plate. The lower end of each supporting tube is fixedly provided with a leg cup (7). The split-type large flange is formed by two semi-annular semi-flanges, and the combination faces of the semi-flanges are symmetrically connected through a connecting piece. The replacing apparatus for the high-voltage cable GIS terminal large flange is easy and feasible; related equipment unit is few; needed time is short; equipment and accessories can be put into operation again without being assembled and disassembled; and a series of tests are not needed, thereby saving time and cost.