The utility model provides a change device of flange steel ring, include: cassette subassembly, cassette subassembly are used for fixing change device of flange steel ring at the flange steel ring, isolation assmbly, isolation assmbly install on the cassette subassembly, and isolation assmbly is moved in order to separate two adjacent flange steel rings along the direction of height of cassette subassembly by external drive. The utility model discloses a change device of flange steel ring can effectively reduce operative employee intensity of labour, improves work efficiency, and the operation process security is high, can reduce the in -process of changing the flange steel ring and have the potential safety hazard.