The diagnostic imaging technique based on ultrasonic Lamb wave can show visually the healthy status of the structure. In this study, a novel diagnostic imaging technique was developed based on the correlation between damage parameters (location, shape, orientation and severity) and Lamb waves signal features (time-of-flight, signal intensity). The structural health was monitored with the assistance of an active sensor network. Both FE simulation and experimental study were conducted to examine a through-thickness crack in an aluminium plate. The diagnostic results have shown high accuracy, which demonstrated the effectiveness of the proposed method.