Relying on the construction project of the east extension line of Nanchang Metro Line 1, aiming at the construction risks such as difficult shield sealing, easy gushing, instability of the excavation face, inclination of buildings (structures), and large deformation of the ground surface and underground pipelines, the key technologies of shield construction in water-rich sand - mudstone complex strata are studied, and the real-time treatment measures for various risks are defined. The research shows that: (1) The "triaxial mixing pile + high-pressure rotary jet pile" method is used for stratum reinforcement at the end, which effectively guarantees the self-stability ability of the rock and soil after the tunnel portal is broken, and provides reliable stratum conditions for the safe entry and exit of the shield machine; (2) The slag is improved with a specific proportion of foaming agent and bentonite, which effectively improves the fluidity, consistency of the slag and reduces the frictional resistance; (3) The precise synchronous grouting method reduces the ground settlement caused by the consolidation of the grouting material during shield construction. According to the deformation of the stratum, the secondary grouting is carried out in a timely manner, which can further improve the waterproofing and compactness of the grouting layer, thereby achieving the purpose of strengthening the tunnel lining and providing guarantee for the long-term stability of the tunnel.