An　n-type　connection　prefabricated　split　column　used　for　an　underground　structure,　　consisting　of　a　prefabricated　steel　reinforcement　bar　concrete　column　(1),　　an　n-type　connecting　piece　(2),　　an　exterior　steel　plate　(3),　　reserved　connecting　steel　reinforcement　bars　(4)　and　a　high-strength　reserved　bolt　(5);　　longitudinal　steel　reinforcement　bars　of　the　prefabricated　reinforced　concrete　column　(1)　entirely　protrude　on　top　and　bottom　surfaces　to　serve　as　reserved　connecting　steel　reinforcement　bars　(4);　　a　steel　reinforcement　bar　cage　of　the　prefabricated　steel　reinforcement　bar　concrete　column　(1)　is　welded　with　the　high-strength　reserved　bolt　(5);　　the　n-type　connecting　piece　(2)　is　connected　to　the　high-strength　bolt　(5)　by　means　of　reserved　bolt　holes　on　two　wings　thereof;　　the　exterior　steel　plate　(3)　is　pasted　on　an　outer　side　of　the　prefabricated　steel　reinforcement　bar　concrete　column　(1),　　and　the　prefabricated　steel　reinforcement　bar　concrete　column　and　connecting　seams　therebetween,　　which　are　in　pairwise　connection,　　are　integrally　wrapped　so　as　to　ensure　normal　use　state　working　performance　of　the　split　column.　The　n-type　connection　prefabricated　split　column　used　for　an　underground　structure　may　be　installed　in　a　key　part　of　an　underground　structure　so　as　to　reduce　damage　to　the　underground　structure　during　an　earthquake.