It is the first time to use outrigger diaphragm wall in Hangzhou area. Based on the practice, this thesis presents main technical points of outrigger diaphragm wall. By the tracking analysis on the practical construction procedure, the whole technological process and technical measures for ensuring construction quality of outrigger diaphragm wall, the excavation depth of basement and the security and stability of foundation pit. The application prospects of outrigger diaphragm wall were presented.