Currently, underground works are being researched and built in cities to reduce and overcome the constant increase of private vehicles. Although it is the most optimal public transport solution in large cities, the construction of underground traffic works also faces many difficulties. For Hanoi urban railway stations, construction by the “top-down” method of open excavation is the optimal choice. At that time, the influence of the groundwater level, the flow of water in the soil will cause the risks of instability of the excavation as well as the risk of damage to the diaphragm wall and the station floor. This article presents the analysis and assessment of the influence of groundwater when deploying solutions to stabilize the diaphragm wall of the underground station of Metro line 3 in Hanoi, thereby making some recommendations to ensure safety during underground construction in Hanoi.