Problems of determination of optimal geometric and constructive parameters of long-length structures are presented. For example, a longitudinal profile of a complicated section is adopted, its components of the stress state and its own oscillation frequencies are determined. The choice of optimal profile parameters is made for the implementation of structures with minimum equivalent stresses, as well as for ensuring maximum dynamic stiffness. It is established that for the determination of equivalent stresses in thin-walled elements, the basic complexity is the calculation of tangential stresses. To simplify the task of optimizing the design parameters, a frequency-mass criterion is proposed. He carried out a refined assessment of the quality of the design and the ability to achieve qualitative properties of the system at minimum mass and high dynamic rigidity. The use of the criterion on the more complex design of the vibration conveyor has been tested. For him, the calculation of FEM own frequencies for different values of constructive parameters is considered. The choice of the final variant of the design is carried out by the value of the frequency-mass criterion.