A defect detection technique based on time-reversal concept is proposed to detect and locate the defects in a plate structure. Time-reversal imaging method is widely use as an advanced, robust data processing and imaging technique in structure health monitoring to detect the defects. Physically, the time reversed signal will retrace its original path precisely, which means that the signals will be refocused back on the source and defects after we record, time reverse and back propagate the wave signal experimentally or numerically. In this paper, a distributed actuator/sensor network is placed on a square homogeneous plate to generate and collect the wave signals in the plate. The time-reversal technique is then used to interpret the physical meaning of the recorded data and image the defects in the plate. Computer simulations are presented to illustrate the feasibility of the technique in this paper.© (2011) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.