In order to study the variation law of ground settlement and settlement of different soil layers during shield tunneling in the water rich strata of Nanchang Metro Line 2, FLAC3D software was used to simulate the three-dimensional numerical simulation of Nanchang Metro Line 2 tunnel, and the horizontal and vertical settlement and displacement nephogram of the ground surface above the tunnel and the settlement law of different soil layers were obtained. The results show that: with the gradual excavation of shield tunnel, the transverse and longitudinal settlement values of the ground surface will gradually increase, and the closer to the center of the tunnel, the greater the transverse settlement value will be, and the longitudinal settlement changes the most at the junction of each excavation step. In the process of tunnel excavation, the ground settlement shows a trend of gradually increasing with the increase of depth, especially when the shield machine is near, its disturbance to the surrounding soil is significantly enhanced, leading to the settlement amplitude in this area is particularly obvious. Through field monitoring and comparison, the overall difference between the model settlement value and the monitoring results is not more than 15%.