The process of phased array theory and image enhancement methods based structural health monitoring is introduced. Phased array theory based structural health monitoring can scan the structure in a certain range of 0°~ 180°. It is realized by controlling the time delay of the excitation signals and the response signals. Because of the imperfect of the original mapped image, the image enhancement method is used to ameliorate the image quality, to enhance image identifiable degrees, and to improve the image resolution. The proposed method is verified by experiment in Al plate. The phased array based SHM method is effective to identify the damage position in the structure and the image enhancement method is able to enhance the mapped image quality.