Abstract: In order to detect the damage of casing boreholes, an acoustic imaging method with a two-dimensional ultrasonic array is presented. Each element of the array independently emits down ultrasonic waves, the echoes received by all elements are sampled and transmitted to a computer on ground surface, where the dynamic migration method is used to form a 2 or 3-dimensional image of the situation in the borehole. The numerical simulation and experiment are conducted that demonstrate a high imaging accuracy with a small number of elements used in array. Since the delay circuits used in the traditional phase array imaging system is not needed in this system, and all data process could be completed in a ground system, the complexity and the volume of system in borehole may be significantly simplified, which is critical to the borehole instrument.