Abstract: Most studies on pile-anchor supporting structures of deep excavation focus on the prestressed anchors and the stability of excavation. However, investigation on the mutual influence and the interaction between the prestress in anchors and the stability of excavation is relatively rare. The object of this paper is to analyze the mechanical performance of pile-anchor supporting structures by using additional stress method and transforming the prestress of anchors to additional stress from soil. A numerical model with prestressing effect of global stability is established for deep excavation pile-anchor supporting structure in this paper and calculation formulas are derived. The results show that the proposed method demonstrates that the variation of prestress has an effect on the global stability safety coefficient of excavation. Furthermore, changes of safety conditions of excavation in each construction stage is also under control, indicating that this method is reasonable and feasible.