Abstract: To investigate the vibration characteristics of a dynamic vibration-absorbing boring bar in deep-hole machining and optimize its damping performance, it is essential to establish a high-precision dynamic model of the boring bar system. Firstly, the boring bar was treated as a flexible beam with non-uniform cross-sections and discretized into multiple rigid-body segments using the multi-rigid-body discretization method. These segments were interconnected via spatial elastic hinges and dampers, forming a coupled multi-rigid-body dynamic model. The system’s dynamic equations were derived based on the Newton-Euler method, and the displacement, velocity, and acceleration responses were solved using the Newmark-β method. Furthermore, to address the issue of unknown parameters in the model, a genetic algorithm was employed in the frequency domain to identify the undetermined parameters based on the acceleration response obtained from impact hammer tests, thereby obtaining a complete dynamic model of the vibration-absorbing boring bar. Finally, the accuracy of the proposed model is validated by comparing the experimental data from exciter tests with the theoretical simulation results.