Abstract: In order to overcome the weakness of the output superposition and the control input coupling of the multi-modal active vibration control, a multi-modal linear auto-disturbance rejection composite active vibration control strategy was designed using multi-loop linear extended stated observer(multi-LESO) plus PD feedback controller. The composite control strategy is independent of the mathematical model of the structure. First, the output superposition and the control input coupling of other modes were considered as a generalized disturbance. The linear ESO of each individual loop can estimate the generalized disturbances, and remove the effects by feed-forward compensation. Then, the linear PD controller for each single mode was designed, respectively. Last, in order to verify the proposed algorithm, the dSPACE real-time simulation platform was used and an experimental platform for the all-clamped stiff-ened panel structure active vibration control was set-up. The experiment results following the several situations demonstrated that the proposed vibration control strategy not only effectively suppressed the vibration excited by first two resonance frequencies of the stiffened panel, but also had the capability of suppression fluctuation caused by uncertain factors.