A novel method is presented to determine the dynamic characteristic of a multi DOF rigid body structure from vibration measurements and coordinates of the transducers. These characteristics include the center of gravity, moment of inertia, and mass; stiffness, center of stiffness and moment of stiffness; damping, center of damping and moment of damping, and corresponding principal values and axes. The method is capable of handling complicated structures with various DOFs, from 2 up to maximum 6. The mass modified matrices are first obtained based on measured vibration data and estimated rigid body modes by data dependent systems methodology