Abstract: A piezoelectric sensors array and active Lamb wave based structural damage imaging method was researched which was helpful to overcome the problems of damage monitoring with multi-mode and mode convention of Lamb wave propagation on plate-like structures, especially on those of composite materials. The principle of time reversal focusing of multi-damage scattering signals was analyzed. Based on this principle, a signal synthesis imaging method based on Shannon complex wavelet and time reversal focusing was proposed. In this method, calculation of time-of-arrival of Lamb wave response signals was an important issue to signal synthesis. A Shannon complex wavelet based time-of-arrival of Lamb wave response signals calculating method was proposed. The signal synthesis imaging method was validated on a carbon fiber composite plate. The result shows that this method could estimate the positions of multi-damages in the same monitoring area efficiently. Compared with the monitoring area of 30 cm ×30 cm, the damage localization errors are no more than 2 cm. It can promote the practical applications of SHM technology.