Taking the coupling interaction between transverse vibration and torsional vibration of input and output end into account, a transversetorsional coupling dynamic analysis model of triple geared drive system of large marine gearbox is established and dynamical coupling equations of transmission system is built according to energybased Lagrance Law. The natural characteristic and dynamic response of this drive system are analyzed using MATLAB software. The result shows that there’s no resonance phenomenon in the system, it has a good dynamic performance and operates almost periodically under the current operating load.