Lamb waves have been used widely for structural damage detection during the past two decades. However, the signals are very difficult to be understood due to their complicated propagation characteristics. Lamb wave imaging approach was established to overcome this obstacle, which can provide an direct indication that where the damage is, what size is the damage and what the shape is. This approach attracts a lot of attention. Hundreds of publications are concerned on this topic. However, there are still some technical problems need to be solved. For this reason, Lamb wave imaging has not been applied in practice. This paper provides a comprehensive review on Lamb wave imaging approaches, which is expected to be helpful for researchers in the field of mechanical damage detection and reliability evaluation.