The invention relates to a shield tunnel reinforcing system of a self-anchored supporting-free member bar and a construction method thereof. The shield tunnel reinforcing system is tightly attached tothe inner side of an existing shield tunnel, and is formed in a manner that multiple annular arc supporting blocks are spliced into a ring, and longitudinal multi-ring assembly is carried out. Blindmortises and tenons are arranged on the two longitudinal sides of a supporting block ring, and the adjacent supporting blocks are anchored through the blind mortises and the tenons; through reinforcing treatment of the area, affected by disturbance or deforming, of the existing shield tunnel, the structure type is simple, stress is reasonable, the advantages of steel part shield tunnel machining,rapid mounting, high bearing capacity, repeated use and the like are sufficiently used, the advantage of a concave and convex mortise and tenon joint structure can be ingeniously used, the effective self-anchored supporting-free member bar reinforcing system is rapidly formed, the deforming can be effectively restrained, structure safety and ovality needs of the shield tunnel can be ensured, and the reinforced shield tunnel has the normal passing capacity.