Abstract: The traditional bolt automatic ultrasonic inspection data is recorded by bar chart. Defects are not intuitive to be checked out. The small defects signal and screw thread signal can not be recognized easily.The position of defects can not be measured and located. Therefore, M mode bar chart and A＼B＼C mode imaging technology are specially designed for bolt automatic ultrasonic inspection. A new ultrasonic data acquisition and analysis softwares developed. It can measure defects location accurately and show distribution of defects directly and plot the small defects signal and screw thread signal clearly. The defect inspection relevance ratio and accuracy ratio are improved greatly by this software.