Summary. This paper addresses the optimization of the structural parameters of the lifting mechanism of the frame for the working equipment in a universal rotary earthmoving trenching and excavation machine operating continuously. The goal is to reduce the efforts in its hydraulic cylinders while maintaining the prescribed kinematics of the mechanism. Structurally, the lifting mechanisms of the working equipment are designed with the hydraulic cylinder positioned above the boom (frame), and the fluid is supplied to the rod chamber of the hydraulic cylinder for lifting. The formulated optimization task aims to design a mechanism that could reach initial and final positions while simultaneously developing minimal peak effort on the hydraulic cylinder rod. Known as a "minimax" problem, this task seeks the minimum value among a set of maximums. Variables chosen include the linear distances from the axis of rotation to the hydraulic cylinder attachment points and the structural angle; a target function is defined. Computational dependencies for determining the design parameters and the force on the hydraulic cylinder rod are presented. Additionally, a constraint on the range of values for the structural angle parameter has been introduced. For calculations, a spreadsheet processor MS Excel with the "Solver" add-on was used. As a result of the optimization for the physical model of the working equipment of the universal rotary earthmoving trenching and excavation machine operating continuously, the parameters for the positioning of the hydraulic cylinder attachment points were found to reduce the load on the hydraulic cylinders by 1.39 times while maintaining the prescribed kinematics of the mechanism. The proposed methodology can be recommended for use in calculations of other lifting mechanisms where the cylinder is positioned above the boom and the fluid is supplied to the rod chamber of the hydraulic cylinder. Keywords: hydraulic cylinder, earthmoving machine, force, working equipment, force calculation, software, link-lever mechanism