Aim\ To study the auto classification and identification method for testing the adhesive state of liner cladded on the inner surface of the rocket motors. Methods\ By means of analyzing the echo signal from the ultrasonic detector

the features of the echo signal as a criteria related to the adhesive state had been extracted with maximum likelihood ratio method modeling to test the rocket motors sample of which inner surface the liner is cladded on . Results\ The results of test coincide with the prefabricated state cladding of the sample and the method of modeling with likelihood ratio is verified. Conclusion\ The method is available for testing the adhesive state of liner cladded on the inner surface of the rocket motors.