Abstract: When ultrasonic wave is used to do the CAT (computer-aided test) for adhesion quality of the piston ring carrier inserts, the returnig echo usually includes both the flow echo and some background noises whichare correlated with the exciting ultrasonic wave. In this paper, a signal processing method based on artificial intelligence is presentead, which is independent of the statistical property of the signal In this method, homomorphism transform technology and fuzzy cognition and decision processes are exploited. The classificatory characteristic used in this method seems more reasonable, more effective and simpler than those proposed before.