Abstract: The coastal areas of Zhejiang are mostly occupied by typical thick silt soft subsoil. The underground space has been rapidly developed and maximized in use as the development of urban construction. The scale of underground structure becomes larger than ever. The design and construction of excavations are facing the issues such as deeper and deeper excavation, more and more massive excavation and more and more complicated surroundings. The construction of super-deep and super-massive excavations needs the application and development of new technology for their support. The author lists 3～5-floor basement structures which are recently designed and constructed in the coastal areas of Zhejiang and also introduces the application and progress of new technology for support of deep excavation, including “two walls into one” diaphragm wall, ultra-deep waterproofing curtain and cut-off wall, underground obstacle disposal, new anchor and cable, deep confined water treatment and top-down construction method, etc.