Abstract: Composite structures play an important role in the fields of aerospace, ocean engineering and rail transit. Due to their defects in impact resistance, real-time on-line impact monitoring technology has attracted more and more attention. In this paper, an impact localization method for stiffened composite plates based on adaptive time reversal focusing imaging was proposed. Firstly, the impact response signal was received by piezoelectric sensor network arranged on the surface of the structure. Then, the narrowband Lamb wave signal of impact response signal was extracted by continuous wavelet transform. And a virtual time-reversal imaging function with impact position coordinates and narrowband Lamb wave group velocity as variables was constructed according to the time-reversal focusing principle. Finally, the virtual time reversal imaging results corresponding to different group velocities were iteratively calculated, and the adaptive time reversal focusing image was obtained according to the maximum pixel curve corresponding to different group velocities to realize impact localization. Drop ball impact experiments were carried out on a stiffened braided composite plate of 800 mm×400 mm (length×width) to verify the effectiveness of the method. The results show that this method can accurately identify the impact location and has a good accuracy in the cases of noise, reducing the number of sensors, and changing temperature.