Abstract: The paper deals with a method to calculate the stable-unbalanced response of a multirotor system,supported on Square Film Damper (SFD) and engaged with the tapered gears,to bending and torsioning vibrations.The influence of SFD and engaging gear of an abnormal structure engine rotor on the stable-unbalanced response of bending and torsion coupling has been studied.A transfer matrix is deduced which is able to determine the gear's unstable response to engaging forces (in 3 directions) and torque.The transfer matrix couples bend and torsion between not only tapered gears,but also abnormal structure and engine shaft.A formula is set up for calculating the potential energy,kinetic energy and energy distribution in the multirotor system.A general computer program is worked out to calculate the engery and the stable-unbalanced response of the multirotor with the tapered gear and SFD.