With the rapid development of shield， construction risk attracts comprehensive attentions in deep foundation pit engineering. Taking as an example the foundation pit excavation construction of 3shield shaft project in South-North Water Diversion main canal project， the WBS method was brought forward to break down the work of deep foundation pits based on the engineering geological conditions and the condition of surrounding in the 3shield deep foundation pits. Then its risk events and factors of construction of deep foundation pits were identified by use of the fault tree method. Finally， the construction risk degrees of all kinds were evaluated and decided in accordance with the general integration risk assessment method based on the AHP method. The method could be used to evaluate the risk degree of similar project.