The utility model provides a shield tunnel segment opening locking device, which belongs to the technical field of shield tunnel construction devices, and comprises a frame structure, a first connecting plate and a second connecting plate, wherein the frame structure is defined by two cross beams which are oppositely arranged and two longitudinal beams which are oppositely arranged; the cross beamcomprises a cross beam outer side plate, a cross beam inner side plate, a cross beam front side plate, a cross beam rear side plate and a cross beam end connecting plate; each longitudinal beam comprises a longitudinal beam outer side plate, a longitudinal beam inner side plate, a longitudinal beam front side plate, a longitudinal beam rear side plate, a first auxiliary connecting plate, a secondauxiliary connecting plate and a longitudinal beam end connecting plate. The first connecting plate is used for sealing the square notch or the rectangular notch in the front side plate of the crossbeam after the cross beam is welded to the containing groove. The second connecting plate is used for sealing a notch defined by the cross beam outer side plate, the cross beam inner side plate, the cross beam rear side plate, the longitudinal beam rear side plate and the longitudinal beam end connecting plate after the first connecting plate is welded. The locking device is welded after being assembled, the structure is stable, and more stable and durable supporting force can be provided for structural pipe pieces.