In order to explore the disturbance mechanism of shield construction on composite strata,taking the coastal composite strata as an example, and relying on the Fuzhou Coastal Line, the disturbance mechanism of shield tunneling in composite strata was investigated.A refined numerical model of shield tunneling was established based on the finite element analysis software ABAQUS, and four parameters were considered, including face support pressure, grouting pressure, jack thrust, and cutterhead torque. After validating the model with on-site monitoring data, the settlement patterns of five composite strata traversed by the shield tunneling in the actual project were examined. The results show that the closer to the excavation area of the shield machine, the greater the disturbance; when the tunnel passes through composite strata, it causes more significant cutting in the softer layer, increasing soil disturbance.