Abstract: The ultrasonic wave detection technology of ultra high pressure crystal vessel is introduced in this paper. And through field test data, the relationship among acoustic path, depth and horizon range is found, the localization method of ultrasonic detection of defects is researched. The method has high reliability and provides a new way of defect detection for the ultra high pressure crystal kettle, and it can also provide a reference for the ultrasonic inspection of the ultra high pressure vessel.