Abstract: Traditional ultrasonic imaging methods, such as the synthetic aperture focusing technique and the time of flight diffraction, can find the position of a defect. However, it cannot image shape and appearance of the defect. The reverse time migration (RTM) method based on wave equation and implying the cross-correlation imaging condition between source propagation field and back-propagation field, which are calculated from measuring data by using finite element or finite differential method, can image shapes and appearances of defects. A multi-elements transducer is used to scan aluminum sample with a slot in our experiment. Comparing with synthetic aperture focusing technique, RTM imaging results show that it is a method superior to traditional one.