Abstract: With the rapid development of urban rail transit, the design forms of subway stations are diversified, and the environment is complicated. Especially the transfer station in urban traffic network, the requirements for foundation pit safety are higher and higher. Based on the excavation project of L-shaped subway transfer station of Hongtang Road Station of Fuzhou Metro Line 5, this paper designs the plugging wall, supporting system, reducing water scheme and excavation sequence of L-shaped foundation pit. On the premise of ensuring the surrounding environment and safety quality, it overcomes the problems of excavation of 36.2m deep foundation pit in water rich sand layer and riverside, and forms a set of feasible construction methods. In actual construction, the maximum ground settlement within 5m around the foundation pit is 13.7mm; The maximum horizontal displacement of diaphragm wall is 22.6 mm; The maximum axial force of the support is 8027kn. All of them meet the safety requirements of the specification.