Abstract: In ultrasonic TOFD (time of flight diffraction) D-scan image, the lateral wave overlaps with the near surface defect wave, which makes it difficult in the testing of shallowly buried defect. In order to solve this problem, a defect testing method based on background clutter suppression is presented. The energy distribution in the image is calculated to determine the clutter wave component. Then the clutter wave is removed to separate the defect signal from the background image. The mathematical model for TOFD signal is established. The principle of clutter wave suppression method is described in details. Artificial defects contained block and the weld test pieces were made and tested. The collected D-scan images with clutter wave suppression were processed. The results show that using the proposed method, the background clutter wave can be removed from the D-scan image and the defect signal can be extracted from the overlapped waves effectively. The defect detection range for TOFD can be improved using the proposed method.