Abstract: The constant thickness steel cement-soil wall constructed by TRD (trench cutting re-mixing deep wall) method is a new type of retaining structure. TRD walls have many advantages, such as wide applicability for multiple strata, good homogeneity of walls and reliability of watertight performance. Therefore, TRD walls used as steel cement-soil retaining structure and ultra-deep impermeable curtain have been successfully applied in many deep excavations in China. The design, construction, test and engineering application of steel cement-soil retaining structure and ultra-deep impermeable curtain constructed by TRD method are introduced.