In order to study the stability mechanism of the double-row steel sheet pile cofferdam system,the finite element method is used to analyze the parameters sensitivity of the backfill,aspect ratio and soil reinforcement of the cofferdam.On this basis,the definition and expression of double-row steel sheet piles cofferdam supporting system redundancy are proposed.The redundancy results of quantitative calculation are consistent with the engineering practice.The above analysis verifies the applicability and feasibility of the redundancy theory in double-row steel sheet piles cofferdam engineering.The practical engineering can optimize the design of the key factors affected the stability of double-row steel sheet-pile cofferdam system according to the redundancy analysis.