Abstract: Excavation of foundation pits may lead to geological losses, modify the in-situ stress field of the original soil, trigger deformation in the outer layers beyond the pit, and adversely affect adjacent composite foundations. Currently, there is a lack of computational methods to quantify the interaction between foundation pit excavation and adjacent rigid pile composite foundations. To address this gap, this study proposes a simplified method for calculating the deformation of a single-point pile-anchor support structure under the influence of an adjacent rigid pile composite foundation. The method integrates: a proposed approach for determining active soil pressure outside the pit, the vertical stress distribution pattern, and deformation characteristics of the single-point pile-anchor support structure. By discretizing (segmenting) the pile body and empolying the matrix transfer method, the simplified deformation calculation method is derived. Furthermore, a theoretical model is established to analyze composite foundation subjected to adjacent excavation. The rationality of the proposed method is verified through comparing numerical simulations with theoretical calculations. Additionally, the impact of excavation on the bearing capacity of composite foundation piles is evaluated based on the calculated pile internal forces. This research provides theoretical support for foundation pit engineering projects near composite foundations.