The following protection measures of construction were adopted on the side of subway in Shanghai Changfeng Commercial Mart that top-down construction method was taken: making the diaphragm walls thicker,delaminating and division and excavating orderly in excavation engineering,reinforcing in pit,remaining rational obligating width of soils near diaphragm walls and excavating the obligating soils.

The top-down construction method is an effective method.

the paper introduces the top-down construction principles,its classification,technique direction and construction method.

Through construction Practice of reverse construction of underground structure, This article describes the technology of foundation pit supporting , earthwork,formwork,steel bars and concrete works and monitoring in the construction,Control measures of cracks of concrete and quality control measures of stability of pit are also be described.

The influential factors of the optimum selection in reversed construction methods was analyzed.

The half against method construction organizes and the quantity supervises and control;

The application of dual-purpose pile in topdown construction can not only save costs,but also make the mechanic condition of substructure walls more rational.