This paper investigates the prediction of residual strength of stiffened composite structure after impact with guided waves-based online monitoring information. Firstly， a piezoelectric sensor network is designed and implemented for the monitored structure， and a structural health monitoring system is established. Local signal difference coefficients are computed along different sensor paths to derive damage indicators， and a damage probability imaging method is employed to identify the location of damage， while the shape factor is estimated to approximate the size of the damage. Secondly， a finite element model is developed for the stiffened composite structure. Feedback from online monitoring results is used to model the damage， and softening inclusion methods are adopted to simulate the damage extent equivalently. By using the progressive failure analysis theory for composite， the residual ultimate strength of the stiffened composite structure after impact is predicted. The effectiveness of the proposed method is validated through a series tests of low-velocity impact， guided waves-based monitoring， and compressive strength， laying foundation for the highest level of application for structural health monitoring.