Abstract: For piston blanks in the mechanical machining process,it is often that practical problems involving in loosing the ring and crazing the combining layers occur.We designed and implemented a system capable of quick detection of the combining quality in ultrasonic.A brief description of the system hardware is given,including a laminar ultrasonic probe,using the models of one transmitter and two receivers for testing.Then we introduced the four stages of the image description to the testing of the combination quality.First,we acquired layer transmission of sound signal amplitude,at the same time to extract the location information in real time detection,piston/ring on the circumference of a circle in the use of a preset pseudo color defect display color table.In the way of the quantitative defection,we used the standard test block contrast method to determine the equivalent defect.Experiments show that this system can realize a synchronous inspection of a single piston of diameter 220 mm or less within 10 s,and it possesses the advantages of simple structure and high quantitative precision as compared with most currently employed testing equipment.