The study investigates the stability of the foundation pit and adjacent bridge piles experiencing prestress loss and subsequent loading compensation of the steel supports. Based on the equivalent temperature-changing method, the prestress loss and compensation are converted into the amounts of temperature change and then applied to the active end of the steel support. The influences of the prestress loss, superstructure loading, yield strength of the support at the pile tip on the displacements, internal forces of the retaining structure and adjacent piles, and the axial support force are analyzed. The results show that the prestress loss will increase the axial forces of the adjacent support while the increments gradually decrease with its distance from the support of loss. The axial force of inner supports and the horizontal displacement of the retaining structure after the loading compensation cannot restore or decrease to the original pre-loss state. The settlement and axial force of adjacent piles caused by successively prestressing loss of the second or third steel supports is larger than that by the synchronous loss. Increasing the pile head loading or reducing the pile tip’s support strength will aggravate the pile settlement caused by prestress loss.