The excavation of the city foundation pit has the characteristics of high construction risk and great difficultly in onstruction. Because of the complexity of the character of underground soil, loading conditions, and construction environment. The monitoring of the haracter of soil, environment, nearby building,and underground facilities has become indispensable links during the construction process. It is the eye to guide construction and also is the required mea- sure to avoid the accident. At present, the foundation pit monitoring, design of engineering, construction have been listed as three basic elements for the quality assurance of deep foundation pit.