The dynamic model of drive system with a face-gear in helicopter transmission was presented.The excitation analysis of rotor to drive system in the cruise and the hover condition was carried out

while the dynamic load coefficient response between face-gears and a pinion in two flight conditions was computed.In the fixed installation and the floating installation

amplitude variation study of dynamic load coefficient between face-gears and a pinion with change of the non-dimensional rotor excitation frequency was developed.It is theoretically and practically significant to the development of helicopter transmission with a face-gear drive in our country.