Shield tail gap monitoring device

The invention discloses a shield tail gap monitoring device. The shield tail gap monitoring device comprises a mounting seat (12) and a shield tail gap monitor (4), wherein the mounting seat (12) comprises a fixed bottom plate (1) which is fixed on a shield tunneling machine shield shell rib plate (11) and a positioning plate (2) which is detachably arranged on the fixed bottom plate (1); and theshield tail gap monitor (4) is fixed on the positioning plate (2), and laser beams of a laser device in the shield tail gap monitor (4) are projected out from a gap (14) between two supporting shoes (9). The shield tunneling machine shield shell rib plate (11) is selected as the mounting position of the shield tail gap monitoring device, and any interference with the mechanical structure of a shield tunneling machine is avoided; and when a hydraulic oil cylinder stretches out and draws back in the normal tunneling process of the shield tunneling machine and an erector rotates in the segment assembling process, normal