Abstract: River-crossing metro tunnels are faced with risks such as leakage and abnormal deformation of the river? bed. Therefore, riverway monitoring during the construction and operation period is essential to ensure the safety of river-crossing tunnels. Taking the river-crossing tunnel of Fuzhou Metro Line 1 as an example, this paper introduces the riverway monitoring work such as underwater environment perception, riverbed topography survey and water flow pattern observation during the shield construction, including monitoring results and early warning analysis, and analyzes the changes of riverbed erosion and deposition in the river-crossing tunnel section during 2009-2018 based on the actual measurement data. The results show that based on the monitored riverway conditions, two alerts regarding water leakage hazards during the shield construction have been issued timely, achieving good monitoring effects; since 2009, the riverbed within the cross-section of the river-crossing tunnel is in a small alternate state of erosion and deposition between years, with the deepest elevation point at -16.06 m in 2018, a gap of only 2.51 m compared to the -18.57 m used for the river-crossing tunnel design. It is recommended that engineering measures such as riverbed protection and branching diversion etc. should be taken, the riverbed safety monitoring mechanism should be established for the river-crossing tunnel section, and emergency protection measures should be prepared to ensure the metro operation safety.