The invention, which belongs to the technical field of bridge engineering, provides a method for calculating the settlement displacement of a bridge foundation by measuring the deformation amount of asupport seat with high precision. A compression stiffness value of each support seat is measured by an experiment; according to design parameters, a finite element model including the support seat isestablished; in the finite element model, the bridge foundation at a certain support seat generates unit settlement displacement and other bridge foundations do no make any settlement displacement, achanging value of a compression deformation amount of each support seat is calculated to form a displacement influence matrix, and an inverse matrix is calculated; and then a precision laser range finder measures a deformation observation value of each support seat of the bridge due to construction and a settlement position and a settlement amount of the bridge foundation are calculated by usinga product of the calculated inverse matrix of the influence matrix and the deformation observation values of the support seats. According to the invention, the settlement position and settlement amount of the bridge foundation are calculated inversely by measuring the deformation amounts of the support seats of the bridge. The method is simple and is convenient to operate; and the theory is reliable.