The composite support technique of prestressed anchor arm and brad has been more and more widely used in foundation pit excavating.Taking a deep foundation excavation at Wangjiazhai,Zhengzhou city as an example,the computation model for the composite support technique of prestressed anchor arm and brad is established using FLAC numerical analysis method.The dynamic process of foundation excavating and support,considering the mutual effect between the support system and soil mass,is simulated.The destabilization of excavation on soil,the displacement change of foundation pit and inner force of brad and prestressed anchor are studied.The conclusions had some reference value for design and construction of the upport technique.