Abstract: Large settlement or differential settlement of shield tunnels built in soft soils occurs in long-term service,affecting performance of segment structure and operating safety. On the background of Foshan metro line 3, this article studied the development law of medium and long-term settlement of shield tunnels in soft soils with different thicknesses and the influence of subsoil reinforcement on long-term settlement by centrifugal model test. The results indicate that the worse and thicker the underlying stratum of tunnel is, the larger the long-term settlement is,and the longer the long-term settlement development is. At the same time, long-term settlement increases under large buried depth; long-term tunnel settlement and ground surface deformation decrease with an increase of foundation soil reinforcement depth, but the decrease extent reduces gradually, and the long-term settlement decreases by 16.7%, 30.2% and 41.3% respectively when the reinforcement depths of foundation soil are 3 m, 6 m and beyond the soft soil, and the ground surface deformation right above the tunnel decreases by 25.4%, 44.9% and 66.3% respectively