Retaining structure is one of the most fundamental measures to guarantee the safety and stability of the foundation pits. Due to the great excavation depth, high ground water level and poor geological conditions of the foundation pits of Xincheng tunnel on the extension line of Jiefang Road in Hangzhou, there exist great difficulties in the construction of the foundation pits. Taking the construction of the foundation pits of Xincheng tunnel on the extension line of Jiefang Road in Hangzhou as example, the paper presents the retaining structure construction technology and the assistance measures adopted in the construction of the foundation pits.