The redundancy theory is introduced into the double-row steel sheet piles cofferdam design. The preliminary framework of the definition and design of double-row steel sheet piles cofferdam supporting system redundancy are proposed. Taking the rod system redundancy analysis for example, alternate path method is adopted to quantitatively analyze for redundancy of the rod system. The results show that the redundancy parameters of lower rods are significantly lower than the upper rods; their failure can significantly reduce the stiffness, strength and stability of cofferdam supporting system; their failure even leads to the destruction of the whole cofferdam to collapse; it is consistent with the engineering practice. The above analysis verified the applicability and feasibility of the redundancy theory for double-row steel sheet piles cofferdam engineering.