With the development of urbanization, the environment of foundation pit is becoming more and more complex, and the deformation control of foundation pit engineering is becoming more and more stringent. At present, the design of foundation pit retaining structure is still controlled by strength, and the design strength is not reached due to the large deformation of conservative design. Based on the improvement of Ritz method based on matrix theory and the principle of minimum potential energy, the deformation coordination condition of retaining pile and horizontal support is considered, the total potential energy equation of retaining pile deformation is obtained, and the deformation of retaining pile is solved. a design method of foundation pit retaining pile based on deformation control is proposed. Finally, the theory is verified by the field measured data of three typical projects, and the results show that the absolute error of prediction increases with the increase of the maximum deformation of the retaining pile, and the average relative error is less than 10% of the maximum deformation.