Large-diameter pipeline water pressure test back blocking plate device

The utility model discloses a back blocking plate device for a large-diameter pipeline hydrostatic test. The back blocking plate device comprises a pressurizing pipeline, a circular blind plate and a sealing plate, a connecting pipe is arranged on the outer side of one end of the pressing pipeline; a limiting ring is coaxially arranged in one end, close to the connecting pipe, in the pressing pipeline; the circular blind plate is located in the pressurizing pipeline and is perpendicular to the inner wall of the pressurizing pipeline, one side of the circular blind plate abuts against the limiting ring, a sealing plate is arranged on the side, away from the limiting ring, of the circular blind plate, and a first reinforcing rib plate is arranged on the other side of the sealing plate; a plurality of fixing devices are arranged on the inner wall of the end, close to the first reinforcing rib plate, of the pressing pipeline in the circumferential direction, each fixing device comprises a fixing frame and a limit