Abstract: Ultrasonic C-scan imaging technology which has advantages of visual defect image and high precision is used far and wide in nondestructive testing. One important process is how to describe the scan path of a complex work. A new type of ultrasonic C-scan system was developed based on CAD/CAM. The system could acquire the scan path via the works CAD files, and it thus reduced the complexity of inputting the scan path and the requirement to the operator. Furthemore, it enhanced the universality of application, increased the efficiency of ultrasonic automatically testing, and had a better effect.