The utility model discloses a reverse circulation clogged slurry door dredging system for a slurry shield, and aims to solve the difficult problems that a slurry door of the slurry shield is clogged when a clogged slurry door cannot be dredged by utilizing a normal slurry circulation system and personnel do not have warehouse entry conditions. The main flow of the construction process is that manufacturing is performed and reverse flushing is performed on the position close to the slurry door relying on the difference between a slurry inlet amount and a slurry outlet amount by adjusting the circulating flow direction of slurry, so that unimpeded slurry circulating flow is recovered. The reserve circulation dredging method for the slurry circulation system provided by the utility model is that the inlet slurry flushes the position close to the slurry door reversely through a slurring circulation bypass loop 2; and outlet slurry is discharged by connecting a slurry inlet main pipe, a bypass loop 3 and an original slurry outlet channel pipeline.