An analytical method and model were investigated on torsional vibration of complex-branch transmission systems in high precision heavy machinery. In this study, application system dynamic theory, torsional vibration topology network model and its analysis technology were introduced for main driving system, including internal and external damping properties, in particularly considering small perturbation induced by microscale effect on the torsional damping and stiffness. Based on above methods, vibration response of input or output could be effeciently calculated and simulation, which was involved with each the rotation shaft as well as the internal torque response. The modal analysis included amplitude and phase response on reference change or load change, bode diagrams, and time domain simulations. Based on conclusion, the study acquired well consistency between the torsional vibration topology network methods and the other classical methods through the calculation example and simulation. Also the new representation could easy be input for the control system and exploit a new ways on real-time control or fault diagnosis monitor for heavy-duty machinery main transmission system.