Abstract: Cutter head wear occurs in metro shield tunnel construction in city deep soft soil stratum. The cutter replacement must be completed in the soil layer reinforcement zone in front of tunnel face. To study the influence of shield cutter replacement on soil mass in front of tunnel face and to obtain reasonable soil layer reinforcement range, 3D numerical model of metro shield tunnel excavation in deep soft soil area is built using PLAXIS-3D finite element software, and the deformation law of surrounding soil during shield cutter replacement is studied. On this basis, the optimal soil layer reinforcement range is finally determined through comparative analysis by orthogonal test method. The results show that during shield cutter replacement, the shield tunnel surrounding soil is prone to large deformation, while the longitudinal one is the least, vertical one the second and transverse one the most; tunnel maximum vertical deformation is on tunnel top, the maximum transverse one is near shield tunnel face, about 22 mm; vertical deformation accumulates over time, the reduction of which requires reinforcement of cutter replacement zone surrounding soil mass; with the increasing transverse reinforcement length, the soil settlement decreases first then increases, and the soil layer transverse optimal reinforcement length is 8 m; after determining the transverse optimal reinforcement length, with the increase of longitudinal and vertical reinforcement length, the vertical displacement of reinforced soil gradually increases, and the longitudinal displacement decreases as the reinforcement length increases, when the longitudinal reinforcement length is increased to 10 m, the longitudinal displacement of ground surface soil is only 0.2 mm; the optioptimal reinforcement range shield cutter replacement zone soil layer is a 10.7 m (longitudinal) × 10.7 m (vertical) × 8.0 m (transverse) cuboid zone.