In order to conquer the disadvantages of undetection, misjudgment and low-efficiency in ultrasonic A-scan testing for rotary parts, an ultrasonic automatic imaging system was developed, and automatic scan device was specially designed for rotary parts. Moreover, the testing software was programmed by LabWindows/CVI, which achieves the acquisition and processing of ultrasonic signals, and displays A, B, C, D and P-scan image. On the basis of storing A-scan data and transforming non-isotropic resolution B-scan image into isotropic one, P-scan imaging is realized. Medium filtering was applied to A-scan signal and C-scan image and the Signal-to-Noise is improved. The experimental results show that this system has well achieved numeralization, automatization and imaging of ultrasonic testing.