Abstract: A physical parameter identification method is presented. For an arbitrarily time-varying system, a series of Hankel matrices are established directly from the combined measurements of displacements, velocities and accelerations (DVA) together with random excitations, which have been obtained through only one experiment of the system. The varying equivalent state space system matrices of structures at each moment are then identified by singular value decomposition (SVD) using random response data. A varying transformation matrix to transform the identified equivalent system matrices into the physical system matrices is developed to determine the mass, stiffness and damping matrices. Finally, a 2DOF spring-mass-damping model with three kinds of time-varying cases is investigated. The results demonstrate the accuracy and effectiveness of the proposed method in identifying the time-varying physical parameters.