As a supporting method the underground continuous wall is commonly used for urban subway structure, and the construction process is largely influenced by the surrounding environment. The forming slot by limited space under the viaduct and lifting the steel cage into the groove can not be normal construction at Huaya station of Changsha Metro Line 5. In this paper, with the side hammer impact drill into the groove, the section folding arm crane lifting steel plate welded connections solutions, and the concrete protection measures of settlement monitoring and grouting reinforcement for the viaduct are put forward. Site construction confirmed the rationality of the construction process, and the experience can provide reference in the similar case.