Abstract: Realizing the problems of outer arc surface crack and outside steel corrosion in existing shield tunnel segments, the paper analyzed the geometric form of crack on outer arc surface at arch waist of segment under different loads by extended finite element method (XFEM). According to the Darcy's law, the water transfer calculation model considering the geometric characteristics of segment crack was established. Based on that, the influence of load crack on the rust layer distribution of outside steel in segment was studied. The results show that:Under external load, the crack form on outer surface of shield segment at the arch waist is like a isosceles triangle, and the crack depth reaches maximum at the edge of segment under the same load; The form of rust layer of outside steel in longitudinal direction is like a "herringbone" curve, and the larger the crack angle, the wider the range of longitudinal corrosion; The form of steel rust layer in segment in circumferential direction is like an elliptical curve, and the non-uniform corrosion coefficient is affected by the crack depth; as the crack depth increases by 20 mm, the non-uniform corrosion coefficient increases by 3%~6%.