Abstract: Nanjing Xuanwu Tunnel, a subaqueous highway tunnel in the centre of the city is a typical geoengineering project in vulnerable environment. The factors which affect construction of subaqueous highway tunnel include not only environmental engineering geology conditions, such a5 variation of soil horizon, distribution of lenssoid body. 1iquefaction of sand, soft soil loss and engineering water hazard, but also urban environment restrain factors, such as cultural landscape, scheme of metro engineering, high buildings and underground line. Furthermore, construction of the tunnel will produce negative effect on urban environment, such as surface subsidence, waste accumulation, variation of water environment, damage of underground pipes and lines and cultural landscape, water contamination and noise pollution, etc. Based on the principle of systematic engineering, the authors analyzed the above problems and evaluated the best tunnel entrance schemes and the best tunnel construction schemes.