The scheme of largediameter shield tunnel, which is characterized by singletube doubleline, was proposed for the construction of Yangtze Rivercrossing tunnels on Line No. 3 and Line No. 10 of Nanjing Metro for the first time in China. The design, construction and related countermeasures during tunneling of Nanjing Metro are proposed. The horizontal crosssection of largediameter rivercrossing shield tunnel constitutes a singletube with doubleline, which is a triplefloor structure. The circular lining ring of largediameter shield tunnel is accordingly proposed, and the longitudinal ventilation is set in the top margin space of tunnel crosssection. The construction practices illustrate that the drill bit replacement under the atmospheric condition is suitable for largediameter shield tunnel (diameter 10～12 m). The experiences accumulated in this project can provide reference for similar rivercrossing Metro shield tunnels with largediameter in the future.