Abstract: Coarser columnar grain leads to awful signal to noise ratio and image resolution , which always produces misjudging of the defects in austenitic stainless steel weld by use of ultrasonic TOFD technique. In order to improve the testing effectiveness, synthetic aperture focusing technique is adopted to process the testing signal extracted by TOFD-D scanning, and influences of apodized function are also studied to optimize the scanning imagery in the research. The results indicate that the signal noise can be depressed by the use of synthetic aperture focusing technique, and the resolution of D-scan image and recognition ability of the weld defects is also enhanced through optimizing apodized function.