Abstract: As there are many artificial factors influencing the evaluation of depth of concrete cracks detected by traditional ultrasonic method, the detection efficiency is therefore very low. In this paper, array ultrasonic imaging method is introduced to study the detection principle and calculation principle of crack depth detection by array ultrasonic imaging method. In addition, a concrete specimen with seven cracks of different depths is designed and produced in the laboratory, and the test of cross-single crack and overall image detection of specimen is carried out. The test results show that:the array ultrasonic imaging method detects the crack depth according to the propagation time of ultrasonic reflected from the seam bottom, and the generated 2D image can display the position of the seam bottom, but not the seam body. The detection accuracy is high and is gradually improved with the deepening of crack depth. Boundary effect should be considered in the detection, otherwise the crack depth cannot be accurately detected. There is a blind area in the detection, and some undetected cracks may exist when the seam bottom is in the blind area.