The invention discloses a GIS shell flange butt joint device. The GIS shell flange butt joint device comprises a fixed clamping piece and a movable clamping piece. A clamping part used for clamping a first shell flange is arranged on the fixed clamping piece. The movable clamping piece comprises a rotating push rod. A pushing part used for pushing a second shell flange in butt joint with the first shell flange in the axis direction of the rotating push rod is arranged at one end of the rotating push rod. The pushing part is opposite to the clamping part. A clamping space used for clamping the first shell flange and the second shell flange is formed between the pushing part and the clamping part. Through cooperative usage of pairwise butt joint devices, the problem that in the prior art, many people exert force to directly push the shell flanges, and consequently force exerting is not uniform can be solved, and the whole butt joint process is stable and labor-saving.