The invention discloses an open type TBM supporting shoe assisting jacking flow reduction tunnel water plugging method. The method comprises the steps that 1, determining a water outlet point of the inner wall of a tunnel, and pretreating the peripheral wall face of the water outlet point of the inner wall of the tunnel; 2, plugging and drainage of the water outlet point on the inner wall of the tunnel; 3, erecting a concrete retaining wall template; 4, pouring a concrete retaining wall; 5, drilling a pressure relief shunting hole; 6, conducting grouting and water plugging on the pressure relief flow distribution hole; and 7, backward grouting and water plugging of the water outlet point of the inner wall of the tunnel. An open type TBM supporting shoe steel structure is utilized, the concrete retaining wall is jacked for flow reduction in an assisted mode, the efficient construction of a 'cement paste and water glass' method is adopted, the plugging is successful and thorough once without leaving the problem, the problem that the tunnel is difficult to construct due to narrow space and limited geographic position of the TBM tunnel is solved, a large amount of labor and material cost is saved, the construction period is shortened, and the efficiency is high.