The identification of structural damage is an important objective of health monitoring for civil infrastructures. System identification and damage detection based on measured vibration data have received intensive studies recently. Frequently， damage to a structure may be reflected by a change of some system parameters， such as the degradation of the stiffness. In this paper， an adaptive tracking technique， Adaptive quadratic sumsquares error(AQSSE) approach， was adopted to identify the structural parameters and their changes when vibration data involve damage events. In this approach， the state equation of motion is considered as a constraint， and the unknown parametric vector is estimated directly. New analytical recursive solutions for the unknown parameter will be derived and presented. Further， an adaptive tracking technique recently proposed will be implemented in the proposed AQSSE approach to identify the timevarying system parameters of the structure and track the variance of structural parameter online. Simulation results for tracking the parametric changes of nonlinear hysteretic and trussed construction are presented to demonstrate the method presented has the capability of tracking the timevarying parameters and detecting the damages， including the damage location and severity which further demonstrate the application and effectiveness of the proposed technique in detecting structural damage， using measured vibration data.