This article presents a dynamic model of the TMM-3M heavy mechanized bridge during the frame lifting stage, which is driven by a hydraulic system, constituting the initial phase of the bridge erection process. The model is constructed as a multi-body dynamic system, taking into account the elastic deformation of the rear outriggers, front tires, and front suspension system. The research model integrates a mechanical system controlled by hydraulic cylinders, with pressure being considered as a variable reacting to external loads during the system's operation. Lagrangian equations of the second kind are utilized to establish a system of differential equations describing the oscillations of the system and form the basis for investigating the dynamics of the frame lifting process. The system of differential equations is solved numerically using MATLAB simulation software based on the Runge-Kutta algorithm. The study has revealed laws regarding the displacement and velocity of components within the system, evaluating the stability of the TMM-3M heavy mechanized bridge during operation. This research paves the way for a comprehensive understanding of the working process of the TMM-3M heavy mechanized bridge, aiming for practical improvements to minimize deployment or retrieval time, reduce the number of deployment team members, enhance the automation of the operation process to reduce the workload for operators