<p>Predicting the global deformation of a combined pile-anchor-strut supporting system in deep foundation pit excavations was challenging due to complex component interactions. A novel analytical approach was proposed to predict the maximum horizontal displacement at the pile top. The total potential energy of the system, including the capping beam, internal struts, supporting piles, anchor rods, and waling beams, was formulated. A key innovation was the explicit incorporation of anchor prestress loss into the energy formulation, an effect neglected in previous models. Applying the principle of minimum potential energy yielded an explicit analytical solution for the maximum pile-top displacement. The proposed method was validated through a case study of a deep excavation in Shenzhen, China. Including prestress loss reduced the displacement prediction error from 29.2% to 9.2% compared to field measurements. The theoretical maximum horizontal displacement at the pile top showed relative errors of 5.1% and 9.2% against field data, and 8.3% and 4.6% against numerical simulations. The calculated overall horizontal displacement curve along the pile depth closely matched field monitoring data. The proposed analytical solution provided a reliable tool for deformation analysis and design optimization of combined pile-anchor-strut supporting systems.</p>