Purpose of research. The purpose of this study is to solve the problem of restoring the external load on the rack– and-beam structural system and to assess the impact on the accuracy of solving the problem of the error of noisy deflections – constructive input data of the computing system.Methods. The main scientific methods used in this study are methods of modeling and identification of boundary conditions, the grid method of regularization of solving inverse incorrect problems. Measurement reduction and approximation methods, methods for evaluating the quality of input data processing, regularization and approximation algorithms using the Lebesgue grid function, and numerical methods are also used.Results. The main result of this work is two theorems about the external load on a rack-and-beam structural system. The existence and uniqueness of the solution is proved. Also, the results are the formulas of Lagrange multipliers in linear Lagrangian approximation and the optimal plan of coordinates of the nodes of the approximation grid for the equation of deflections of the beam of the fourth and fifth degree with Chebyshev alternance. An assessment of the quality of the approximation of the external load on the rack-and-beam structure by the values of the target parameters was carried out.Conclusion. This article proposes a method for restoring the external load on a rack-and-beam structure using the results of solving the inverse Cauchy problem for the equation of deflections of a beam with minimizing the influence of the error of noisy input data.